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AUDIO-VISUAL CONSERVATION
at The LIBRARY tfCONGRE9S

VI"

Packard Campus

for Audio Visual Conservation

www.loc.gov/avconservation

Motion Picture and Television Reading Room
www.loc.gov/rr/mopic

Recorded Sound Reference Center
www.loc.gov/rr/record

tlHf

No 1

ride Film — Color — Sou nd

James J. Finn. Editor

:i H, Kutian :

"THE LENS THAT PUTS PERFECTION IN PROJECTION

THE ILEX F:2.5
PROJECTION LENS

Definitely Superior in Every Detail of Its

Performance

This statement is made unqualifiedly. It is based on the reports of users.

The superior brilliance, greater sharpness and detailed definition of the
Ilex stand out forcibly when compared to any other make.

When Ilex is used the realistic portrayal removes all the effort and strain
and allows the patron to relax in full enjoyment of the play. Only with
Ilex is maximum projection efficiency possible.

And to add to the advantages of Ilex there is the new Adjustable Fea-
ture. A feature which insures exact screen coverings, overcoming entirely
unsightly slopover or incomplete covering.

To sum up: — the Ilex F:2.5 represents the very latest scientific advance-
ments in projection lens construction. Acquaint yourself with its details
and performance. Write us today. » ;s

ILEX OPTICAL COMPANY

ROCHESTER (Established 19 lO) NEW YORK

25<

Sign of Perfection

SURE -FIT!

for
SIMPLEX PROJECTORS

Ready for quick deliv-
ery to all parts of
United States and
Canada

KAPLAN PROJECTORS

Suitable for

Vitaphone — Movietone

and all other sound
systems

Manufactured

and

Distributed

by the

Sam Kaplan

Manufacturing and

Supply Co., Inc.

At Last— The Perfect Reel

The most troublesome factor of the projection room — the
need for a precision reel — is now solved for all time. It has
everything you have been asking for:

1st — Broken parts replaced by sections — all you
need is a screw driver and a few seconds of
time.

2nd — Saves money. You don't have to buy a com-
plete reel if you break a section.

3rd — Runs easily and smoothly. Absolutely no
friction. Saves wear and tear of film.

4th — Original in conception and design. A new
idea in reel construction.

' -

Now Being Used by Thousands of Theatres and
Recommended by Expert Projectionists Everywhere

Sam Kaplan Manufacturing and Supply Company, Inc.

729 Seventh Avenue NEW YORK CITY

November 1929 Published monthly by Man-call Publishing Corp., 45 West Ahth St.. N. Y. City. Entered as

\r ■ i m' i second class matter Oct. 25, 1927, at Post Office. New York, N. Y., under the act of

Vol. J, INo. 1 March 3, 1879.

Canadian Representative: H. N. Elliott, Suite 11, 27 Sherwood Ave., Toronto, Canada

25c per copy
$2.00 a year

oSJj|l|gB89

S pea ki nqj)LR@s u I ts

-pea cHtf i s :

UNIVERSITY

STPAND

ga»e"tY

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comw

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EAST

9TH

963

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AND-

Aug<

17 1 a

'29

, icer Corp»»

*°* t0r ' vin£ tbat «e give * t

eV^in^ *&?£ it

f^fo^ee-^ disc,

;?taoTament xs iffipr0ved tne rUgSednese afisfied ^ "tem

seems to ^9 ^Ta ^prlled and 8^e optxcal b*^

war* mucTa P^Lreeatol^ ^rpesPecial^ ted all * ilm.
^ ar9nVand are *°fuC?ion of same. eixm ^ sound-on

S&SS. **" or ^ U a gj^e and

Y0U fses^ecause, a Jd e xnter
opinions-

, eincerel^ ^urs,
THE CO^ODOKE THE

ML/MM

For Houses up to 2,000 Seats : Type 2MDA, Synchronous Disc and Sound on Film $3,500 ; Synchronous
Disc Only $2,500 .... For Houses up to 4,000 seats : Type 4MDA, Synchronous Disc and Sound on Film
$4,500; Synchronous Disc Only $3,500 .... The Pacent Film Attachment when sold separately is $750.

Two Attachments needed with each Pacent Disc System.

PACENT REPRODUCER CORP.

Film Center Bldg.
NEW YORK, N. Y.

The Motion Picture Projectionist

November, 1929

MEET THE

SENATOR

PRICE

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00 per

= Set

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with all necessary
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Combination Automatic
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Built like a -watch— It is compact, noiseless and
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Made specifically for sound equipment— Tested
and endorsed by Fox— Stanley— Poli Circuits-
Lower in price than any other.

Made and Guaranteed by

Sentry Safety Control

13th and Cherry
PHILADELPHIA

1560 Broadway
NEW YORK

November, 1929

The Motion Picture Projectionist

STATEMENT OF THE OWNERSHIP, MAN-
AGEMENT, CIRCULATION. ETC., RE-
QUIRED BY THE ACT OF CONGRESS OF
AUGUST 24, 1912. of

THE MOTION PICTURE
PROJECTIONIST,

published Monthly at New York, N. Y„ for
October 1, 1929.

STATE OF NEW YORK ) „.
COUNTY OF NEW YORK ] ss-

Before me, a Notary Public in and for the
State and county aforesaid, personally appeared
James J. Finn, who, having been duly sworn
according to law, deposes and says that he is
the Editor of THE MOTION PICTURE PRO-
JECTIONIST, and that the following is, to the
best of his knowledge and belief, a true state-
ment of the ownership, management (and if a
daily paper, the circulation), etc., of the afore-
said publication for the date shown in the above
caption, required by the Act of August 24, 1912,
embodied in section 411, Postal Laws and regu-
lations, printed on the reverse of this form, to
wit:

1. That the names and addresses of the pub-
lisher, editor, managing editor, and business
managers are: Publisher, Mancall Publishing
Corp., 45 West 45th St., New York City;
Editor, James J. Finn, 45 West 45th St., New
York City; Managing Editor, none; Business
Manager, James J. Finn, 45 West 45th St.,
New York City.

2. That the owner is: Mancall Publishing
Corporation, 45 West 45th St., New York City.

Boone Mancall, 45 West 45th St., New York
City.

3. That the known bondholders, mortgagees,
and other security holders owning or holding 1
per cent or more of total amount of bonds, mort-
gages, or other securities are: None.

4. That the two paragraphs next above, giving
the names of the owners, stockholders, and se-
curity holders, if any, contain not only the list
of stockholders and security holders as they ap-
pear upon the books of the company but also,
in cases where the stockholder or security holder
appears upon the books of the company as
trustee or in any other fiduciary relation, the
name of the person or corporation for whom such
trustee is acting, is given; also that the said two
paragraphs contain statements embracing affiant's
full knowledge and belief as to the circumstances
and conditions under which stockholders and se-
curity holders who do not appear upon the books
of the company as trustees, hold stock and se-
curities in a capacity other than that of a bona
fide owner; and this affiant has no reason to
believe that any other person, association, or corpo-
ration has any interest direct or indirect in the
said stock, bonds, or other securities than as so
stated by him.

5. That the average number of copies of each
issue of this publication sold or distributed,
through the mails or otherwise, to paid subscribers
during the six months preceding the date shown
above is . . . (This information is required
from daily publications only.)

JAMES J. FINN,

Editor.
Sworn to and subscribed before me this 1st
day of October, 1929.

NATHAN REIGROD
[Seal] (My commission expires March

30, 1931.)

10,000 Installations by 1930

Production at the big Western Electric
factories having speeded up considerably,
it will be possible to wire 10,000 theaters
by the end of 1930, according to H. M.
Wilcox, operating manager for Electrical
Research Products, Inc. The latter com-
pany now has more than 200 service men
stationed at 26 service stations through-
out the country.

Don't Scrape Emulsion

Emulsion should not be scraped off the
sound gate. Scraping scratches the polished
surface which easily again becomes coated
with emulsion. The proper way to remove
emulsion from the gate is to use a damp-
ened cloth, which does not harm the
surface.

Singing scene from "Hearts in Dixie," Fox Movietone film

14% LESS

HERE is a strip of movie-
tone film. Each frame has
been reduced 14% to make
room for the sound track.
You must have more light
to project this sound picture
on the screen in the same
size and intensity as a silent
full-sized frame. More light
means more juice. National
Projector Carbons produce

more light on higher inten-
sity . . . the positive carbons
form deep, well-rounded
craters . . . the National Pro-
jector Oro-Tip Negative
Carbons do not pencil. When
your theater is equipped for
sound be sure that you have
an ample supply of National
Projector Carbons to give
you all the light you need.

National Projector Carbons

NATIONAL CARBON COMPANY, INC.
Carbon Sales Division, Cleveland, Ohio

Unit of Union Carbide j and Carbon Corporation

Branch Sales Offices
New York, N. Y. Pittsburgh, Pa. Chicago, 111.

San Francisco, Calif.

Birmingham, Ala.

Complete your sound equipment with a

f?BEST"

Rewind Pulley

Takes the place of space collar on Reel

shaft — Crank is not Removed

Manufactured by

BEST DEVICES CO.

2108 PAYNE AVE.

P.'lit 13.00 at all dealers

CLEVELAND, O.

The Motion Picture Projectionist

November, 1929

QUALITY

The

INTENSITY

Type F R

High Intensity Arc

For Motion Picture Projection

Hundreds of successful installations tell their story of
the best possible projection at lowest operating cost

HALL &

24 VAN DAM STREET

CONNOLLY, Inc.

NEW YORK CITY

A Rectifier Built for Use with Sound

Features

25 amps at each arc
during change-over

30 to 40 amps for
Spotlight

Nothing to wear out

Accessible

Durable

Small installation cost

Can be used on any
A. C. Supply

Low cost of operation
No moving parts

Type M. P. 25-25

Advantages

Less Initial Cost
Saving of Current
High efficiency 80-86%

No special Booth re-
quired

Readily accessible

Lower Maintenance
Cost

No Special Wiring
Required

Fireproof

Shockproof. No live
parts exposed

Noiseless

No Oiling

Easy to Operate

Operate Two Projectors from One Rectifier

Your Supply House Can Tell You All About This Machine

FOREST ELECTRIC CORP., 272 New St., Newark, N. J.

1 "

ft >

IP* n

-•:-,-,—

PI5 ;

MESTRUM'S combina-
tion lamphouse car-
riage and pedestal brace for Simplex
projectors insures perfect rigidity and
eliminates all vibration. Can be used
with old-style, 3-point base or with
new-style, 5-point base, especially with
Movietone and Vitaphone. Installed
quickly without machine work.

MESTRUM

514 West 46th St. N. Y. City

THE BIOSCOPE

The Leading Journal of the British
Cinematograph Industry

20th Year of Weekly Publication

Contains a complete section each week
for the special benefit of Projectionists.

Cash prizes awarded for original ideas
published. Specimen copies 18 cents.

Annual Subscription 7 dollars 50

The Bioscope Publishing Co., Ltd.

8-10 Charing Cross Road, London. W. C. Eng.

November, 1929

The: Motion Picture Projectionist

4=1=1:

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"3 may be dumb, but I
know when the lights
goes out!"

"Say, listen Leona, if you haven't saw Ravoni
Bologni in the 'Occasional Bride' down at the
Gaiety, you simply gotta see that show. It's
one of the swellest pitchers I ever seenl Thai's
where I went yesterday, only I started to see
it the day before yesterday, like I was going
to tell you, but something broke down and
they couldn't go on with the show. And mebbe
I wasn't madl It was right where things begin
to get exciting, if you know what I mean, when
it broke. Well, mebbe things like that used to
happen when grandpa was a flaming youth,
but I always say there ain't no excuse for it
nowadays, so I walked right out. I should pay
to get in and then stay there without seeing
anythingl And anyway, someone got up and
said they was sorry but the show couldn't go
on, and wouldn't we get tickets at the door
and everything would be all right again next
afternoon. Imagine anything as crazy as thatl
So when I got in the lobby there was the fella
that runs the joint passing out the rain checks
and I walks up to him and says, 'Listen, what
do you think this is, 1885 or something? I come
here to see a pitcher not to sit in the dark!'
'I am sorry, madam,' he says to me, 'but the
accident was unavoidable, accidents will hap-
pen sometimes.' 'O, yeh?' I says to him, 'Well,
listen, I may be a home girl, but I have been
around enough to know that moving pitcher
shows ought not to bust down likeiooi flivvers!'
Oh, did I lay him to the daisies I So he says,
'But, madam, you don't understand I' 'Oh, I
don't?' I come back at him, 'Well, listen, Wis-
dom Tooth, I may be dumb, but I know when
the lights goes outl' With that, I walks out on
him cold and only leave him a dirty look to
remember me by. But I took the rain check
anyhow, dearie, because I always say it's all
right to be proud as long as you don't carry
it too far. So I went back yesterday and every-
thing was fixed up all right again. And believe
me, kid, if it hadn't a been that joint wouldn't
never have got no more of my shekelsl

"But mebbe that isn't a swell pifcherl — where
Ravoni Bologni — that's her sweetie, see, —
comes in and finds her alone with her husband,
mebbe he don't DO things I Gosh, I think he's
simply gorgeous, so listen, kid, you simply
gotta see that pitcher!"

IHERE are two practical
ways of taking out insurance against an inter-
rupted or a completely stopped show: the
purchase of good equipment and the use of
reliable maintenance service. Today the Na-
tional Rebuilding and Repair Division is a vital
and strongly forged link in the chain of com-
plete theatre service. From coast to coast Na- 1
tional Repair Shops are completely equipped
to take care of any job — from supplying an
emergency mechanism on a moment's notice, |
to the thorough rebuilding of projector or
generator. These shops are staffed by expert
machinists and electricians schooled in modern
factory methods. Throughout every phase of
their craft none but genuine repair parts are
used. If overhauling is needed in your booth, I
don't wait until an emergency! When you get
an estimate on the job from your nearest
National Branch you'll know why expert
maintenance service is one form of insurance
you can't afford to be without.

And if an emergency does arise — if a genera-
tor goes dead or a mechanism "freezes," there's
no greater mental relief for an Exhibitor than
the knowledge that a phone call to his nearest
National branch will get those needed repairs
as rapidly as is humanly possible to make
them . . . for National Repair Experts and their
Exhibitor friends work under (he cam" slogan —
"The Show Must Go Or

ir>¥X2Mzi*mizwAnm'JAUMVJjxmiuii*i

The Motion Picture Projectionist

November, 1929

JUST OFF THE PRESS

/^kUR catalog showing the many beautiful
^-^ effect slides for all types of presenta-
tions and special staging is ready at last!
They are now being mailed out to several
thousand projectionists all over the country

Our slides used with the
BRENKERT F-7 Master
Brenograph.

One of these valuable

who have requested copies.

catalogs will be sent to
you immediately if you
will write to us.

This catalog is an important contribution
to projection technique. You will be behind
the times unless you keep yourself posted on

these presentation effects.

WORKSTEL STUDIOS

151 WEST 46TH STREET NEW YORK CITY

The Invisible, Noiseless Changeover for SIMPLEX— MOTIOGRAPH F.— SURE FIT

HOLMES— SUPERIOR Projectors

AUTOMATIC SHUTTER CONTROL

and

3-WIRE CIRCUIT
FOOT SWITCH

(Miniature power house)

Switch floor brackets
now available

Designed for the simplest

installation and changeover

dependability with all sound

equipment.

Installed by
Roxy — Keith — Stanley — Schwartz
Loew — -Fox — Wilmer & Vincent

Ask your dealer or write

DOWSER MANUFACTURING CORP.

225 Broadway, New York City

November, 1929

The Motion Picture Projectionist

"A Best Seller"

It Is—

Without question : The most
important book ever published
in the field of Motion Picture
Projection.

Even the most skilled Projec-
tionists can get valuable oper-
ating tips from its 400 pages
of text and 130 odd illustra-
tions.

Written by Rudolph Miehling
— a Projectionist acknowl-
edged an expert on sound —
an engineer of national reputa-
tion.

PPfpC $£00 We Pay
1 rVlV^IL O Postage

ORDER NOW

THE MOTION PICTURE PROJECTIONIST
45 West 45th Street, New York City

Gentlemen:

Please send me Rudolph Miehling's book, "Sound
Projection." Enclosed find check (or money order)
for $6.00.

Name

Street

Town

Stare

Contner-Blue Seal Universal Lens
Adaptor and Aperture System

Your picture always the
full screen area.

No mask needed on
screen. Optically cor-
rect.

Used by leading theatres
in the United States and
Canada.

Used by Loews — Publix
— Radio-Keith — Cen-
tury Circuit — Wilmer &
Vincent — Stanley Cir-
cuit.

For further information
ask your dealer, or write

Blue Seal Products Co., Inc.

262 Wyckoff St. BROOKLYN, N. Y.

PERFECTION IN
CARBONS

For Low Intensity Projection

Smooth, Steady Burning

Wonderful Light

After many experiments our factory has produced
the new "Noris HS" low intensity carbon which, we
believe, cannot be surpassed by any other brand on
the market.

Send for trial samples.

HUGO REISINGER, Inc.

25 MURRAY STREET

NEW YORK

The Motion Picture Projectionist

November, 1929

1 V

.-.'■.

I*'

THE INTERNATIONAL
PROJECTOR

MADE IN THE LARGEST AND
OLDEST PLANT IN THE WORLD
DEVOTED TO THE MANUFACTURE
OF MOTION PICTURE PROJECTORS

SIMPLEX SUPREMACY

IS THE RESULT OF TWENTY-FIVE
YEARS EXPERIENCE IN THE SELEC-
TION OF MEN — METHODS AND
MATERIALS

International Projector Corp.

new york, n. y.

C 1 o

November, 1929

The Motion Picture Projectionist

Storage Battery Standards

THE storage battery is a valuable
adjunct of the sound motion picture
system. Just now there is a move-
ment afoot among workers in the sound
picture field to provide the necessary ele-
ment which will eliminate the use of stor-
age batteries with sound projection appa-
ratus. Whether these efforts are success-
ful or not remains to be seen, yet the re-
sults of this work will take nothing away
from the proven dependability of the stor-
age cell nor diminish its effectiveness in
those fields in which it has performed
long and valuable service.

It cannot be denied that the storage bat-
tery has many characteristics which are
not to be dimmed by even the best of bat-
tery eliminators. Nothing that has thus
far been revealed in the development of
battery eliminators has indicated that it
will match the proven reliability of the
storage battery. Certainly the storage bat-
tery is noiseless and there is a total ab-
sence of line fluctuations. There are other
characteristics in its favor too well known
to need mention here.

The following listing of "standards"
has been adopted as official by the Ameri-
can Institute of Electrical Engineers1, to
whom we are indebted for permission to
publish them.

The standards in this section apply to
storage batteries of the lead-acid type and
of the nickel-iron alkaline type. They are
suitable for large and small batteries in
either stationary or portable service. These
standards conform to accepted usage.

Classification

Storage batteries are classified as sta-
tionary or portable batteries on the basis
of construction. Stationary batteries are
those designed for service in a permanent
location. Portable batteries are those de-
signed for convenient transportation dur-
ing service. Portable batteries may be
used for service in a permanent location.

Construction

Storage Battery. — A connected group
of two or more electrochemical cells for
the generation of electrical energy in
which the cells after being discharged may
be restored to a charged condition by an
electric current flowing in a direction op-
posite to the flow of current when the bat-
tery discharges. Common usage permits
this designation to be applied to a single
cell used independently.

Storage Cell. — The unit of the battery,

consisting of positive and negative plates,
separators, electrolyte, and container, for
the generation of electrical energy and
capable of being recharged by an electric
current.

Active Materials.- — Materials of plates
reacting chemically to produce electrical
energy during the discharge. The active
materials of storage cells are restored to
their original composition, in the charged

1 February 16, 1928.

condition, by oxidation or reduction proc-
esses produced by the charging current. In
the charged condition the active materials
are as follows : —

Lead Acid Nickel-iron

Plate Cells Alkaline Cells

Positive Lead peroxide Oxides of nickel

Negative Sponge lead Iron

Grid. — A metallic framework for con-
ducting the electric current and supporting
the active material".

Positive Plate. — The grid and active

material from which the current flows to
the external circuit when the battery is
discharging.

Negative Plate. — The grid and active
material to which the current flows from
the external circuit when the battery is
discharging.

Electrolyte. — An aqueous solution of
sulphuric acid used in lead cells and of cer-
tain hydroxides used in nickel-iron alkaline
cells. The concentration of the solutions
varies somewhat with the type of cell, its
use, and condition. The electrolyte of
charged cells at 70 deg. Fahr. (21 deg.
Cent.), will ordinarily fall within the fol-
owing nominal limits of specific gravity : —

Lead Acid Nickel-iron

Cells Alkaline Cells

Maximum 1.300 1.230

Minimum 1.200 1.160

Separator. — A device for preventing

metallic contact between the plates of op-
posite polarity within the cell.

Group. — Assembly of a set of plates of

the same polarity for one cell.

Element. — -The positive and negative
groups with separators assembled for a
cell.

Couple. — The element of a cell con-
taining two plates, one positive and one
negative. This term is also applied to a
positive and negative plate connected to-
gether as one unit for installation in ad-
jacent cells.

Jar. — The container for the element
and electrolyte of a cell. Specifically a
jar for lead-acid cells is usually of hard
rubber composition or of glass ; but for
nickel-iron alkaline cells it is a nickel-
plated steel container frequently referred
to as a "can."

Tank. — A lead container, supported by

wood, for the element and electrolyte of a
cell. This is restricted to some relatively
large types of cells.

Case. — A container for several cells.
Specificially wood cases are containers for
cells in individual jars ; rubber or com-
position cases are provided with compart-
ments for the cells.

Tray. — A support or container for one
or more cells.

Terminal Posts. — The points of the
cell or battery to which the external cir-
cuit is connected.

- In certain types of batteries the active ma-
terial is enclosed in containers which are held
in place by the grid.

Cell Connector. — A conductor used for
carrying current between adjacent cells.

Counter Electromotive Force Cells. —

Cells of practically no capacity used to op-
pose the line voltage. Frequently called
"Counter cells."

End Cells.— The cells of a battery
which may be cut in or out of the circuit
for the purpose of adjusting the battery
voltage.

Pilot Cell. — A selected cell whose tem-
perature, voltage and specific gravity of
electrolyte are assumed to indicate the con-
dition of the entire battery.

Capacity
Ampere-Hour Capacity. — The number
of ampere-hours which can be delivered by
a cell or battery under specified conditions
as to temperature, rate of discharge and
final voltage.

Watt-Hour Capacity. — The number of
watt-hours which can be delivered by a
cell or battery under specified conditions
as to temperature, rate of discharge and
final voltage.

Time-Rate. — The rate in amperes at

which a battery will be fully discharged in
a specified time, under specified conditions
of temperature and final voltage. Exam-
ple, the eight-hour rate or the twenty-min-
ute rate.

Voltage
Open-Circuit Voltage. — The voltage of

a cell or battery at its terminals when no
current is flowing. For the purpose of
measurement, the small current required
for the operation of a voltmeter is usually
negligible.

Closed- Circuit Voltage. — The voltage

at the terminals of a cell or battery when
current is flowing.

Average Voltage. — The average value
of the voltage during the period of charge
or discharge. It is conveniently obtained
from the time integral of the voltage curve.

Initial Voltage. — The voltage of a cell
or battery at the beginning of a charge or
discharge. It is usually taken after the
current has been flowing for a sufficient
period of time for the rate of change of
voltage to become practically constant.

Final Voltage. — The prescribed volt-
age upon reaching which the discharge is
considered complete. The final voltage is
usually chosen so that the useful capacity
of the cell is realized. Final voltages vary
with the type of battery, the rate of the
discharge, temperature, and the service in
which the battery is used.

Polarity. — An electrical condition de-
termining the direction in which current
tends to flow. By common usage the dis-
charge current is said to flow from the
positive or peroxide plate through the ex-
ternal circuit. In a nickel-iron alkaline
battery the positive plate is that containing
nickel peroxide.

Polarization. — The change in voltage
at the terminals of a storage cell, when a
specified current is flowing, equal to the
difference between the actual and the equili-

The Motion Picture Projectionist

November, 1929

brium (constant open-circuit condition) po-
tentials of the plates, exclusive of the / R
drop.

Charging and Discharging

Charge. — The conversion of electrical
energy into chemical energy within the cell
or battery. This consists of the restoration
of the active materials by passing a uni-
directional current through the cell or bat-
tery in the opposite direction to that of the
discharge. A cell or battery which is said
to be "charged" is understood to be fully
charged.

Charging Rate. — The current ex-
pressed in amperes at which a battery is
charged.

Constant-Current Charge. — A charge
in which the current is maintained at con-
stant value. For some types of lead bat-
teries this may involve two rates called the
starting and the finishing rates.

Constant Voltage Charge. — A charge
in which the voltage at the terminals of
the battery is held at a constant value. A
modified constant voltage system is usually
one in which the voltage of the charging
circuit is held substantially constant, but
a fixed resistance is inserted in the battery
circuit producing a rising voltage charac-
teristic at the battery terminals as the
charge progresses. This term is also ap-
plied to other methods for producing auto-
matically a similar characteristic.

Boost Charge. — A partial charge,
usually at a high rate for a short period.

Equalizing Charge. — An extended
charge given to a battery to insure the
complete restoration of the active materials
in all the plates of all the cells.

Watt-hour Efficiency. — (Energy effi-
ciency).— The ratio of the watt-hours out-
put to the watt-hours of the recharge.

Temperature
Reference Temperature. — The capacity
obtained from a storage battery on dis-
charge varies with the temperature of the
electrolyte. The following standard refer-
ence temperatures are established.

(1) The temperature of electrolyte at
beginning of discharge shall be 25 deg.
cent. (77 deg. fahr.). No limit is placed
on the temperature attained by the elec-
trolyte during discharge.

(2) The ambient temperature on dis-
charge shall be from S deg. cent, to 8 deg.
cent, lower than the temperature of the
electrolyte, on the beginning of discharge.
The ambient temperature shall be kept
constant throughout the discharge.

Temperature Coefficient of Voltage. — ■
The change in open-circuit voltage per de-
gree (cent.) change in temperature.3

Temperature Coefficient of Capacity. —
The change in delivered capacity expressed
as a percentage of the ampere-hour or watt-
hour capacity per degree (cent.) change in
temperature between specified limits.

Critical Temperature.— The tempera-
ture of the electrolyte at which an abrupt
change in capacity occurs.

Rating of Batteries
General. — Batteries are usually rated
in terms of the number of ampere-hours

0 This is but a few tenths of a millivolt and
must not be confused with the effect of tem-
perature on changes in voltage resulting from
polarization and / R drop when charging or dis-
charging.

which they are capable of delivering when
fully charged and under specified condi-
tions as to temperature, rate of discharge
and final voltage. For different classes of
service, different time-rates (See definition
of time-rate) are frequently used. For
comparing the capacities of batteries of dif-
ferent size but of the same general design,
it is customary to use the same time-rate,
and a comparison based on the different
lengths of time they will discharge at the
same rate is not recommended as it is mis-
leading.

Misrating. — A battery which fails to
deliver its rated capacity on the third suc-
cessive measured cycle of charge and dis-
charge under specified current rates, tem-
perature of electrolyte, specific gravity, ard
final voltage, shall be considered to be im-
properly rated.

Trickle Charge. — A continuous charge
at low rate approximately equal to the in-
ternal losses and suitable to maintain the
battery in a fully charged condition. This
term is also applied to very low rates of
charge suitable not only for compensating
for internal losses but to restore intermit-
tent discharges of small amount delivered
from time to time to the load circuit.

Finishing Rate.— -The rate of charge
expressed in amperes to which the charging
current for some types of lead batteries is
reduced near the end of charge to prevent
excessive gassing and temperature rise.

Discharge. — The conversion of the
chemical energy of the battery into elec-
trical energy.

Reversal — Change in normal polarity
of a storage cell.

Local Action or Self-Discharge. — The

internal loss of charge which goes on con-
tinuously within a cell regardless of con-
nections to an external circuit.

Floating. — A method of operation in
which a constant voltage is applied to the
battery terminals sufficient to maintain an
approximately constant state of charge.

Specific Gravity of Electrolyte. — The
electrolyte of lead acid batteries increases
in concentration to a fixed maximum value
during charge and decreases during dis-
charge. The concentration is usually ex-
pressed as the specific gravity of the solu-
tion. This variation of specific gravity
of the solution affords an approximate in-
dication of the state of charge.

The specific gravity of the electrolyte in
nickel-iron alkaline batteries does not
change appreciably during charge or dis-
charge and therefore does not indicate the
state of charge. The specific gravities,
however, are indication of the electrochem-
ical usefulness of the electrolyte.

Gassing. — -The evolution of oxygen or
hydrogen, or both.

Efficiency

Efficiency. — The ratio of the output of
a cell or battery to the input required to
restore the initial state of charge under
specified conditions of temperature, current
rate, and final voltage.

Ampere-Hour Efficiency. — (Electro-
chemical Efficiency). — The ratio of the am-
pere-hours output to the ampere-hours of
the recharge.

Volt Efficiency. — The ratio of the aver-
age voltage during the discharge to the
average voltage during the recharge.

S. M. P. E. Toronto Meeting

THE Fall meeting of the Society of
Motion Picture Engineers which was
held at the Royal York Hotel in Toronto,
Canada, October 7-10 inclusive, was a con-
spicuous success in many particulars. Mem-
bers of the Society were most enthusiastic
about the .recent Convention and the gen-
eral opinion is that it will be hard to better
its sessions. It has been the good fortune
of the Society to have had every successful
development in motion picture work given
an advance showing at its meetings.

While the papers on sound pictures
played a very important part at the
Toronto gathering, their contents touched
mainly on refinements to existing apparatus
and technique rather than in revealing any
outstanding new development. For the most
part the papers read dealt with highly
technical problems of the making and
showing of motion pictures.

Many Interesting Papers

Among the papers read which are of
particular interest to those interested in
projection work were: "The Illusion of
Sound and Picture," by John L. Case, RCA
Photophone, Inc. ; "Theatre Acoustics," by
S. K. Wolfe, E. R. P. I.; "The Optics of
Motion Picture Projection," by Professor
Arthur C. Hardy, Massachusetts Institute
of Technology; "The Film Perforation and
Means for its Measurement," by W. H.
Carson, Agfa Ansco Corp. ; "Surface
Treatment of Sound Film," by J. I. Crab-

tree, C. E. Ives, and O. Sandvik; "A New
Method of Blocking Out Splices in Sound
Film," by Messrs. Crabtree and Ives ;
"Characteristics of Loudspeakers for Thea-
tre Use," by D. G. Blattner, Bell Tele-
phone Labs. ; "Optical Problems of th<-
Wide Film," by Dr. W. Rayton, Bausch
& Lomb Optical Co. ; "Some Practical
Aspects and Recommendations on Wide
Film Standards," by A. S. Howell and J.
A. Dubray, Bell & Howell Co. ; "Some
Aspects of Reverberation," by E. W. Kel-
logg, General Electric Co. ; "Water Cooling
of Incandescent Lamps," by Dr. N. T. Gor-
don, General Electric Co. ; "Operating
Characteristics of High Intensity Arcs," by
A. C. Downes and D. B. Joy, National
Carbon Co.; and "Camera and Projecto*-
Aperture in Relation to Sound Pictures,"
by Lester Cowan, A. M. P. A. & S.

One subject which seemed to be the gen-
eral topic of discussion among Society
members was the advent of wide film, a
development which offers many problems
for the engineer. Because wide film has
been only recently exhibited, there was not
sufficient time for the preparation of papers
on the subject before the Society Meeting.
However, it is certain that the next Meet-
ing will include many papers on the subject
of wide film both in the production and
projection fields.

J. I. Crabtree of Eastman Kodak Co.,
is the new president of the S. M. P. E.,
succeeding L. C. Porter, Edison Lamp
Works.

THE T II I II I)

SERIES ON QUALITY REPRODUCTION

WESTERN ELECTRIC

-A* «**

to quality reproduction

yet an

Exclusive Feature

of the Western Electric
Sound System

TALKING pictures are recorded at a
speed of 90 feet per minute. They must
be reproduced at exactly the same speed.
Variations in speed cause the pitch of voice
and music to rise or fall.

A musical ear will detect sudden changes
in pitch caused by a change in speed of
only one-half of one per cent. If the speed
is not held within this small limit, quality
reproduction is impossible. Ordinary motors
will not answer this purpose.

Western Electric has solved the problem
by the use of a specially designed motor
control which holds the motor speed within

one-fifth of one per cent. This is an exclu-
sive Western Electric feature.

Its operation is automatic, requiring no
attention. The worry and trouble of attempt-
ing to control the speed of reproduction
is eliminated.

The motor control box is just one of a
number of refinements found only in the
Western Electric Sound System which make
quality reproduction a fact. The exhibitor
will find that this control and other fea-
tures are distinct aids in putting over a
talking picture with the quality demanded
by the public.

Quality Reproduction means Western Electric Reproduction

Westen

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Distributed by

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250 West 57th Street, New York, N. Y.

Member of Motion Picture Producers and Distributors of America, Inc — Will H. Hays, President

The Motion Picture Projectionist

November, 1929

FULCO PROJECTOR — Ernemann Design

CONVENIENCES

' I 'HE Fulco Projector em-
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Projectionists recognize and
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Particularly is this true with
reference to adjustment facili-
ties and the ease and conven-
ience with which it is possible
to make any and every adjust-
ment quickly and surely.

The Fulco is the one Projector
above all others completely
under Projectionist control and
susceptible of delicate changes
of adjustment even while in,
action.

In a large measure this ac-
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Projection results always no-
ticeable where Fulco Projec-
tors are used.

MOIST AIR completely
banishes heat. It has
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without drying it up.

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A
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ATLANTA — 146 Walton St. LOS ANGELES — Film Ex. Bldg.

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November, 1929

The Motion Picture Projectionist

Waves and Wave Motions

By J. A. Dowie

Chief Instructor, National Radio Institute, Washington, D. C.

TO be able to understand how sound
waves (speech and music) can be
reproduced from a radio receiving
set located many miles away from a broad-
casting station, a study of wave motion
and the characteristics of waves is
essential.

A wave may be defined as a disturbance
in some elastic substance, the disturbance
having a regular period or frequency both
as to time between repetitions and as to
its strength.

The erroneous impression exists in many
minds that it is the medium which actually
travels away from the point where the dis-
turbance causing the wave is created, but
it should be clearly understood that the
medium as a whole remains stationary, and
the wave action of the individual particles
is purely local.

For example : If we lift one end of a
straight rope and shake it briskly up and
down, a wave is thus started in the rope
which will travel down its length. It is
evident that in this case the wave consists
of a successive and individual vertical mo-
tion of each point of the rope. If the rope
is shaken twice, two waves will be started
which travel away to the other end, keep-
ing always the same distance apart. If
the shaking of the rope is repeated rhyth-
mically, a continuous wave motion is
started which transmits the energy im-
parted by the hand to the other end of the
rope.

Analysis of Waves

The high points of a wave are called the
crests, and the low ones troughs. The dis-
tance between two successive crests is the
wavelength, the height of the crest above
the trough, the amplitude, while the speed
at which the wave apparently travels is
called the frequency. The frequency is ex-
pressed by the number of waves passing a
given point each and every second. The
above terms, "wavelength," "amplitude,"
are graphically illustrated in Figure 2 and
it is well to bear their relationship clearly
in mind.

Science has gradually realized that all of
the perceptions of our senses are due to
waves generated in a substance which seems
to permeate everything, and which has
been called the ether. That such a sub-
stance actually exists has long been doubt-
ed, but the study of the phenomena in con-
nection with the transmission of heat, light
and electricity shows that they are all due
to wave action which cannot be explained
unless by the assumption of a medium for
these waves to travel in.

All ether waves travel with the same ve-
locity of 300,000,000 meters per second,
which is equivalent to about 186,500 miles.
They differ widely in their wavelength,
however, and are known to range from a
wavelength of 150,000 meters which are the
longest radio waves yet encountered, to a
wavelength of 500 billionths of a meter.
All these waves are apparently identical in
nature.

Some of them can be discovered only
by the most delicate instruments, some of
them by the sensations of what we know
as heat and light ; and in the latter case,
the different colors are again differentiated
by wavelength variation. Some penetrate
so-called opaque objects, and are known
to act as X-rays ; some are invisible to our
eyes and to our senses, yet produce cer-
tain pathological effects upon the body such
as sun-stroke, and it has been claimed

ROPE

Figure 1

softening of the bones, and finally, some
can be detected only by radio apparatus.

Sound Waves

Sound is a wave motion of the air, not
of ,the ether. If a bell or a piano wire
be struck, the bell or the wire will vibrate
many hundreds or even thousands of times
per second. Every vibration hits the sound
in the air a slight blow which starts a
wave in the same manner as in the experi-
ment with the rope. From the source of
the vibration, these sound waves travel
outward in every direction, gradually be-
coming weaker as the distance from the
source increases.

In the delicate mechanism of the human
ear, the vibrations impinge against the ear-
drums and cause them to vibrate at the
same speed, thus producing what we know
as sound. The greater the amplitude of
the original vibration, the further will the
wave be transmitted ; hence, the amplitude

M>lncir,j Po.y £e,zonc/ ,

VoAie

1V<»uqk
Figure 2

of a sound wave corresponds to the loud-
ness of a tone. What is known as the
pitch, on the other hand, is a result of the
number of vibrations per second or fre-
quency.

The lowest tones which the human ear
can hear and distinguish correspond to
about 30 vibrations per second, the highest
to about 18,000 vibrations per second.
Anything above or below these values are
audible not as a musical note but as a
noise.

A vibrating source producing a single
frequency is said to produce a pure tone.
The frequency of the source is referred to
as the pitch. Musical tones, however, as

produced by bowing a violin or striking a
piano, do not consist of pure tones but ordi-
narily consist of a particular frequency and
in addition a number of other frequencies,
known as harmonics. Harmonics are fre-
quencies which are multiples of a given
frequency known as the fundamental.
Thus, if we strike a piano note, the funda-
mental frequency of which is 500 cycles,
we would also find present in the air sound
waves having frequencies of 1,000, 1,500,
2,000, 2,500, 3,000, 3,500, etc., cycles.

In radio work, we like to refer to the
frequency having a value twice that of the
fundamental as the second harmonic, the
frequency having a value three times the
fundamental as the third harmonic, and so
on. While the pitch of a musical tone is
determined by the frequency of the funda-
mental, the tone quality or timbre, as it is
sometimes called, depends upon the ratio
of the amount of energy in the various
harmonics to that in the fundamental. It
is this ratio which enables you to deter-
mine, even though you may not be able to
see the instrument, whether or not the tone
is produced by a piano, violin or singer.

The ordinary land telephone affords the
means of reproducing sound waves at a
distance far greater than the original wave
will cover. The scund wave strikes a metal
diaphragm which is thereby set in vibra-
tion. To the diaphragm is attached an
electrical contact composed of small pieces
of carbon rather loosely held together,
through which a current is flowing. When
the carbon particles are compressed by the
motion of the diaghragm the resistance of
the particles is decreased because they are
brought in closer contact with each other,
and a greater amount of current flows in
the circuit.

Transmitting Apparatus

This current is then made to pass
through an electromagnet at the other end
of the line and the magnetic charge in the
magnet will vary in accordance with the
current changes. The magnet acts upon
the other diaphragm at the receiving end
which vibrates in synchronism with the
transmitting diaphragm and generates
sound waves corresponding to the original
one.

The apparatus used to send forth
through space the electromagnetic waves
which carry speech or musical vibration
in any broadcasting system consists of
three essential parts. The first of these
is a radio frequency generator which pro-
duces uninterrupted constant-amplitude al-
ternating current of exceedingly high
frequency. The second is a modulator,
which controls the amplitude of this high
frequency alternating current and varies
it In strict accordance with the sound vi-
brations to be transmitted. The third is
the radiator, or antenna system, which will
aid in converting the sound modulated radio
frequency current impressed upon it into
corresponding electromagnetic waves in the
ether or space.

The Motion Picture Projectionist

November, 1929

Coast Technicians Strive for Standard
Aperture Size

HOLLYWOOD motion picture stu-
dios are now composing all vital
elements in sound-on-film pictures within
an area of 0.620 by 0.835 inches altho con-
tinuing to photograph the whole frame.
This is in accordance with specifications
recently recommended by the Academy of
Motion Picture Arts and Sciences, Techni-
cians' Branch, acting jointly with the Tech-
nical Bureau of the Association of Motion
Picture Producers, the American Society
of Cinematographers, the Pacific Coast
Section of the Society of Motion Picture
Engineers and the California Chapter of
the American Projection Society.

Theatres which restore the full screen
image from sound-on-film pictures have
been notified that to secure the maximum
image size in 3 by 4 proportion they should
use projector apertures whose size would be
0.600 by 0.800 inches on the basis of pro-
jection on the level, the horizontal center
of the aperture coinciding with the hori-
zontal center of the S. M. P. E. standard
aperture.

Nationwide Survey

The recommendations and action by the
studios followed the revelation through a
nationwide survey that theatres are using
a wide variety of aperture sizes in project-
ing sound-on-film pictures. It was also
found that an increasing number of thea-
tres are restoring the full screen propor-
tion through the use of a smaller aperture,

lenses of one-half inch shorter focal length,
and various re-centering devices. As only
two studios were composing to allow for
this, the result was that in many theatres
part of the heads and feet of characters
were cut off in projection. The recommen-
dations of the technical societies are de-
signed to correct this serious condition and
were chosen as the best means of the pro-
jector aperture sizes among a number of
large theatre chains.

Studios which are now marking the
ground glasses of their cameras to conform
to the recommended practice are : Para-
mount-Famous-Lasky, Metro-G oldwyn-
Mayer, United Artists, Pathe, Universal,
R. K. O., Tiffany- Stahl, Mack Sennett,
Darmour, and Educational. The Fox Stu-
dio markings are the same width but allow
.04 inches more height.

Committees representing the motion pic-

325,000 Engaged in Pictures

More than 325,000 persons in the United
States, secure their wages from pictures,
according to a recent estimate. More than
100,000,000 persons attend picture shows
weekly, it is declared, with the 20-odd
thousand theatres of the United States said
to have an aggregate seating capacity in
excess of 18,000,000. The 100,000,000
figure, it is said, represents about a 100
per cent increase over attendance of a few
years ago.

Restoration of Aperture to 3
x 4 Proportion on Basis of
Dimensions Recommended
by Academy of Motion
Picture Arts and Sciences.

Circle Represents a
Head Close-up.

A-Original "B and H" Silent
Aperture— .720"x9375".

B-A with Sound Track— .085".

C-Recentering of B —

— Account of Sound Track.

D-C Recentered — with Camera
Aperture as shown — .620" x
.835".

E-Head Reduced to meet projec-
tion requirements of Proj.
Aperture in F.

F-New Proj. Aperture, size .600"
x .800", inside Camera Aper-
ture showing Head reduction.

G and H represent cutting of
Head in Projector by im-
proper Framing.

ture technical organizations in Hollywood
are also studying the problems of standard
release print practice and screen illumina-
tion under the sponsorship of the Academy.

Projectionists Aid

In addition to the participation of the
Los Angeles chapter of the American Pro-
jection Society as an organization in send-
ing out questionnaires, discussing the prop-
osition and endorsing the final recommen-
dations, a number of projectionists were
active personally. Sidney Burton, presi-
dent of the Los Angeles A. P. S. chapter,
E. W. Anderson and Albert Feinstein were
members of the joint committee from the
different organizations which drew up the
resolution. David Koskoff, as secretary of
the A. P. S. chapter, also gave much help
in collecting data on projection conditions
in theatres throughout the United States
and Canada.

By V. E. Miller, Paramount-Famous-Lasky

Suggests 51 mm. As the
Ideal Film Size

THE sound track has encroached upon
the picture area to a very awkward
extent. The Movietone frame and the 70
m.m. Grandeur film are two unhappy ex-
tremes. This wide picture seems to claim
favor as an approach to the visual range
of the eye. We believe this is a mistaken
promise. Let us not forget that the great
range of the human vision is provided us
as a means of protection, but that the choice
field of vision is very limited.

Effect on the Eyes

A simple experiment will demonstrate
that when we select a prospect, the area
of critical interest is very narrow, and be-
yond this, is merely a conscious retinal
periphery. All forms of pictorial art de-
mand a narrow, but pleasing, projection,
and we venture that there is little artistic
appeal in an excessively wide film. We
should carefully distinguish between a
larger picture, in the taking, and a wider
screen.

A larger initial picture may certainly
have many advantages, provided there are
no mechanical difficulties in the projection.
Its value may be understood by an exag-
gerated comparison — if we imagine a mo-
tion picture, of the dimension of a lantern
slide, projected to the size of the standard
screen, we would have a picture of incom-
parable beauty and smoothness of grain,
and all other blemishes would be propor-
tionately reduced.

51 mm. Standard

It is logical to assume that the picture
must, eventually, be provided with a space
for the sound track; this could be done in
the positive only without disturbing the
standard proportions of the negative. If
the industry insists, however, on a change,
the ideal dimension appears to be that sug-
gested by Westerberg, 51 m.m. wide, with
the picture 36 m.m. x 22^ m.m.

It is terrifying to contemplate scrapping
the present standard equipment, but any-
thing so revolutionary as the "talkies" de-
mands equally radical changes in the ma-
chinery to produce them artistically. —
Lewis W. Physioc in The International
Photographer.

November, 1929

The Motion Picture Projectionist

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The Motion Picture Projectionist

November, 1929

Television — Present and Future

By Thomas W. Benson

TELEVISION will develop along
two rather well-defined lines. We
now have operating on regular
schedule several radio stations that are
transmitting pictures experimentally which
may 'be received by those properly equipped
to do so. These pictures are crude, admit-
tedly, are too small and lack detail to the
point where they have but meager enter-
tainment value. What of it? The radio
spark transmitters of fifteen years ago also
lacked entertainment value in exactly the
same sense, yet the results obtained by
these crude amateur experiments provided
the nucleus for much subsequent serious
work.

Present results attained with television
apparatus evoke much criticism, which is
usually couched in the general statement
that television will not be here for five,
ten, or twenty years. The most important
objections raised are that there are too
many mechanical difficulties to be over-
come, no channels to carry the signals, the
equipment is too expensive, etc., and the
rather disheartening circumstance about
these attacks is that those who have faith
in the future of television must admit
them to be well-founded — that is, when ap-
plied to television for individual home use.

Television in the Theatre

However, I do not believe that the real
television will come first to the home for
the reception of pictures by radio nor as an
attachment to the telephone — another long
sought-for ideal. It is my opinion that the
expense attached to television equipment
will be prohibitive for the bulk of home-
owners. Those firms in the front rank of
television development are inclined to the
belief that television will first be intro-
duced as a form of entertainment within
the theatre.

In this way we can see the possibility of
installing equipment which would be en-
tirely beyond the financial means of the
individual in the theatre where perform-
ances would go on on schedule just as the
motion picture is exhibited today. The
present-day motion picture theatre will be
tomorrow's television theatre. In this
fashion will television be introduced, and
the expenditure of from thirty to forty
thousand dollars will not be unreasonable
if results comparable with motion picture
results of today are attained.

We might compare this line of develop-
ment with that of the radiophone. With
the perfection of the radiophone transmit-
ter, it was thought that everyone would
soon carry a small portable set and would
telephone anywhere, anytime by radio.
This has not come to pass, yet the individ-
ual can pick up his or her telephone and
"go on the air" from a central transmitter
or can go personally to one of the radio
broadcasting stations. And so in television.
The individual may not own a television
receiver but he will be able to enjoy a

television performance at his neighborhood
movie house at a nominal charge.

Sources of Material

It is obvious that the large television
receiver must receive pictures from two
sources. We have the usual entertainment
source, namely, filmed stories. It is likely
that the earliest transmissions will be from
films for reasons which will shortly be
explained. The second source is the pic-
turing of events the instant they occur,
which, by the way, is true television. The
latter method is, of course, exceedingly dif-
ficult with the apparatus now available, al-
though it has been accomplished under lab-
oratory conditions.

To the eye a picture has two dimensions
■ — height and width — and consists of nu-
merous shades of light and dark. The
present means of electrical communication
will transmit only one dimension — that is,
they- will transmit only such matter as can
be re-created by variations in the current
flowing over the channel of communication.
The problem of television, then, resolves
itself into reducing the two-dimensional
picture to one dimension and transmitting
the changes in tone of the picture. The
usual practice is to reduce the picture to
one having all width and no height, that is,
practically speaking.

Equipment Used

This sounds impossible; but if we were
to consider a picture cut into a number of
strips crosswise and then these strips ail
joined end to end, we would have the same
highlights and shadows as were in the orig-
inal picture, yet we would have reduced
the picture to one dimension — that of
width. It would not resemble in the least
a picture; but we can transmit the varia-
tions in shade along this strip and at the

receiving end arrange to cut the strip into
lengths and, by arranging them one above
the other, rebuild the picture.

It all may seem like magic, and although
we do not actually cut the picture up, the
effect is the same, as the action must be
carried out at least 16 times a second in

order to get even fair results. Speeds of
20 per second wil^ doubtless be used.

Let us consider slitting up a film for
transmission. This process is known as
scanning and is shown in Figure 1. The
film to be transmitted is projected to any
desired size — let us say one foot square —
by means of a regular projector. A cool-
ing system on this projector is advisable
so that the film may not become hot and
buckle. The film moves smoothly instead
of intermittently as in a standard motion
picture projector.

Back of the aperture through which the
picture is projected is mounted a disc that
has holes drilled through it in a circle
near the edge. These holes should be
square and are as large as the strip desired
is wide, and are separated, the distance
equal to the width of the projected picture.
Behind the disk is mounted a photo electric
cell of the alkali metal type, the properties
and operation of which have been described
at length by Samuel Wein in these col-
umns.1 Little more about these cells need
be said here except that the current flow-
ing through the cell will vary in direct
proportion to the amount of light to which
it is subjected.

16 to 20 Scenes a Second

Now let us start the transmitter. The
light from the arc in the lamphouse throws
the picture on the disc. The disc is started
revolving, and as the first hole sweeps
across the top of the picture, the varying
lights and shadows across the strip fall
upon the photo electric cell and are tran-
slated by the cell into varying electric cur-
rents. Now the film moves slightly and
the next hole in the disc travels across a
strip just below the first strip, and the
lights and shadows thereon are reduced to
equivalent electric currents. Again the film

1 August, September, October, December issues,
1928; January, April, July, September. October,
1929.

Fig. 1.

Suitable method

for trasmitting

movie film by

television

PHOTO
CELL

DISK

November, 1929

The Motion Picture Projectionist

is moved and the third hole covers the
third strip in exactly the same manner.
This action continues until the whole pic-
ture is viewed.

Transmit Sound and Scene

In practice, this action is speeded _ up
until from 16 to 20 scenes are covered in a
second. Thus it is seen that the "eye" of
the television apparatus (the photo electric
cell) sees the scene only as a long strip
and transmits it as such.

It is fairly clear that the film, if it car-
ries a sound track, could be run through
a sound head and the sound transmitted as
well as the scene. This would give us ideal
television.

Scanning the Image

Let us consider for a moment how the
scanning of an actual scene is accom-
plished, for here it is obvious that we can-
not move the subject being transmitted as
in the case of movie film. The system
that will be used for such purposes is
illustrated in Figure 2 which shows an ob-
ject illuminated by arcs while a lens
reduces the scene to the size of a scanning
aperture before the disk. Behind the disk
is the photo electric cell that picks up the
varying light densities of the scene.

However, it will be noted that the disk
in this case has the holes drilled spirally.
Thus, as it is rotated, the outermost hole
covers the top strip of the picture, the next
hole being nearer the center scans the next
strip, and so on till the whole scene is cov-
ered or viewed. Here also the action must
be speeded up to the minimum of 16 per
second.

Types of Disks Used

Note particularly the difficulties intro-
duced. With the film transmitter, the holes
in a line permitted the use of any size disk
found desirable, for the disk could be

speeded up so that as many holes as neces-
sary could pass over each scene. That is,
if we desired the scene slit into one hun-
dred strips, the film was moved one hun-
dredth of its height between the passing of

Fig. 2 — Scanning
method employed
for television trans-
mitting

each hole, and the disk was run fast
enough to get one hundred holes past for
each scene.

With the spiral disk this condition does
not hold. We can only determine the num-
ber of strips the picture is divided into by
the number of holes, and the disk revolves
but once to scan a scene. Suppose we
wish to cut the scene into 100 strips:—
this would mean that 100 holes would have
to be drilled in the disk, and with a small
picture — say, only two inches square — these
holes would have to be two inches apart.
Thus, a disk some 200 inches in circum-
ference would be required, or more than
5 feet in diameter.

Were we to increase our requirements to
a picture similar to the one discussed with
film transmission, we would need a disk
some 35 feet in diameter. This method of
transmission is, then, far from perfect, but
a possible solution is to photograph the
events with a movie camera and then trans-

TUBE

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Fig. 3— Principle of operation of glow tube screen for theatre
showing of television

mit the film. This no doubt will be done
until improved systems of direct scanning
are available.

Transmitting the Picture
Without going into lengthy technicalities,
we will now consider transmission of the
picture. This deals with the frequency of
the currents necessary to transmit the pic-
ture. It will be readily understood that
the light coming through the hole in the
scanning disk at any instant is the sum of
the light values of that portion of the scene
being viewed, and any small detail in that
area will be identified only as it affects the
total light from that area. Hence, it can
be said that the total area exposed at any
given instant comprises a picture unit, and
only details as large as picture units will
be transmitted. Since each change of light
gives a change in current, and the scanning
disk recognizes areas as large as the hole,
the maximum number of changes of light
possible would occur where each succeeding
picture unit was black and white. From
this it can be shown that the maximum
frequency to be transmitted is equal to half
the number of picture units ; and the mini-
mum will be equal approximately to the
scanning rate, or 16 to 20 scenes a second.
We will find, then, that should we desire
to split the film being projected into strips
that will give us good detail, we will
require at least 80 strips to the inch of
the enlarged picture, resulting in 6,400 pic-
ture elements per square inch, or more than
9 million for the whole picture.

Current Requirements

With each scene being transmitted in
l/20th of a second, it can be shown that a
current frequency of 9 million cycles per
second would be required to successfully
transmit the picture. However, this may
not appear entirely impossible when we
consider that by selecting proper back-
grounds, shooting scenes differently and
limiting the number of actors, we can elim-
inate much of this need for detail; and it
is the writer's belief that the frequency
actually required need not exceed 2 million
cycles.

This figure presents communication engi-
neers with a very difficult problem, for
most wire channels are taxed at 20,000
cycles and require correction. While short
wave radio channels might handle the nec-
essary frequency at the extremely short
waves, they are unreliable for the purpose.

It is necessary that some method be de-
veloped to handle these frequencies, and it
(Continued on page 34)

The Motion Picture Projectionist

November, 1929

Carbon: Its Properties and Uses in Motion

Picture Projection

By Engineering Dept., National Carbon Co.

THE motion picture projector is a
very reliable piece of mechanism.
Although subjected in some in-
stances to intense heat, it will, if properly
taken care of, last a long time and give
excellent service. All parts of the ma-
chine should be kept clean and well oiled.
Connections should be kept tight, carbon
jaws cleaned regularly to prevent cor-
roding, condensers cleaned daily, and, not
least of all, the proper sizes and grades
of projector carbons should be used.

It has been our experience that a very
large percentage of complaints registered
have not been due to the quality of the
carbons, but, rather, to operating condi-
tions, or to the fact that wrong carbons
were being burned. Perhaps some space
devoted to operating precautions will be of
value. Let us take the old type ot low
intensity lamps first.

D. C. Low Intensity Lamps

These lamps are generally known as
the old-type lamps. The usual complaints
received on carbons used in these lamps
are: (1) Arc traveling or wandering
(2) Burned-out or burned-back craters
(recessing) (3) Lip on the upper car-
bon (4) Mushroom points, i. e., a button
formed on the negative (5) Excessive
spindling, and (6) Sputtering at the arc.
Let .us take up these points in the order
given.

Arc Traveling or Wandering

We will confine ourselves for the time
being to machines operated on direct cur-
rent. As has already been stated, before
the advent of Silvertips, the common
practice was to use a large diameter
regular cored or solid projector carbon in
the lower holder. This negative carbon
in most cases was slightly smaller in
diameter than the positive ; although in
others, the same diameter was used.
With the large blunt point on the nega-
tive it was not possible to keep the arc
steady and in one spot. It wandered all
around the point. (See Fig. 18 showing
34" cored upper and ¥&" cored lower).

This resulted in poor light on the
screen. Then, too, the large negative
carbon in some instances masked or ob-
structed some of the light from the

ggm

Figure 20

Figure 18

Figure 19

positive crater and this naturally decreased
the illumination. Obviously the thing to
do was to use a negative of smaller
diameter. A plain carbon would not carry
the current, so metal was applied to pro-
duce the carbon now known as Silvertip.
Burn-out or Burn-back Craters
Usually this condition is caused by
either one of or a combination of three
things': (1) too high a current (2) too
low a current and/or (3) the use of

Figure 21

Left: Fig. 22; Right: 22 A

carbons too large in diameter. If the
current is too high, the force may blow
the core out. (Fig. 19.) If too low, or if
the wrong combination is being used — such
as % x 12" cored upper and a %" cored
lower at an arc amperage of, say, 35 — the
current is so low that the soft core ma-
terial is consumed more rapidly than the
surrounding shell and the result is a very
deep or recessed crater in the positive
carbon. Under such conditions, the core in
the negative carbon will invariably burn
back. (Fig. 18).

In the first mentioned case, the remedy
is to cut the current down to the proper
amount ; and in the second and third cases
to increase the current to the proper
amount. Damp carbons will also cause
the core to burn back or recess.

Lip on Upper Carbon

This condition is caused by an improper
setting of the carbons. The negative car-
bon has been set too far forward (Fig. 21).

Figure 22 shows the blunt point obtained
when the negative carbon is set too far
back. Obviously most of the light will
be thrown downward rather than forward
through the condensing lenses. Figure
22A shows good crater formation.

Mushroom Points

If too short an arc is drawn, a "button"
is formed on the tip of the negative car-
bon (Figs. 23 and 24). This is caused
by the deposition of particles of carbon
from the positive on to the point of the
negative carbon and this phenomenon will
happen with any style or make of negative
carbon. The condition referred to is com-
monly spoken of as "freezing of the arc."
The proper arc length to draw is about
Ya" to ^2". When striking the arc, the
points should be separated quickly, other-
wise you may shatter the positive crater
or graphitize both points.

Excessive Spindling

One cause of excessive spindling is that
the carbons are being overloaded. Figures
25 and 26 show a Yi cored positive carbon
overloaded, and a i%" Orotip solid nega-
tive carbon overloaded.

Care should be taken that the combina-
tions of carbons which our engineers have
worked out and have recommended .are
used. Spindling may also be caused by
poor contact in both positive and negative
holders. Both upper and lower jaws or
holders should be cleaned out regularly so
that the contacts will be smooth.

Sputtering at the Arc

Sputtering at the arc may be caused by
carbons not being properly set or trimmed,
or by too short an arc ; more frequently,
though, it is caused by a damp carbon.
Carbons are porous and absorb moisture.
They are baked at extremely high tempera-
tures in our factory ; when they leave the
factory they are thoroughly dry. In ship-
ment, however, they may be exposed to
damp weather, or at point of destination
stored in a damp basement. Carbons should
be kept in a dry place. A great many
projectionists have formed the habit of
laying a few carbons on top of a rheostat
in order to expel any moisture that might
have been absorbed after leaving the fac-
tory. Others put a trim in their lamp-

Top: Fig. 23; Bottom: Fig. 24

ovember,

1929

The Motion Picture Projectionist

houses before burning. Either practice is
a good one and is to be recommended as
a clamp carbon may chip at the crater in
addition to causing a sputtering arc.

It might be added here that carbons are
not perishable : they will be as good ten
years from now as they are today. If
they have absorbed water only, they can
be dried out in the manner just referred
to. However, if a chemical has been spilled
on them, they may be rendered worthless,
depending on the nature of the chemical.

A. C. Low Intensity Lamps

Of the few carbon complaints made, those
which are common to direct current — such
as excessive spindling, arc traveling,
burned out cores, sputtering, etc. — are
likewise common to the alternating cur-
rent arc, and the remedies previously pre-
scribed will eliminate them. For A. C.
work the same diameter is recommended
for both upper and lower carbons. In
all cases the carbons should be cored.
Care should be taken that the upper carbon
is set at an angle of approximately 20°
from the vertical, while the lower carbon
is vertical (Fig. 27).

Unless watched closely, the lower carbon
will mask the crater of the upper carbon ;
consequently the maximum amount of
light does not reach the condensers. After
every reel the arc should be lengthened,
thus permitting the burning off of the lip
and making possible the V-shaped crater.

Mirror or Reflector Arc Lamps

AS has already been emphasized, the
proper combinations of carbons should
always be used. The contacts should be

«»»8S$W» ■■; :■■'■

Figr

Figure 26

clean. In the horizontal type of mirror
arc lamp, i. e., the type in which both
positive and negative carbons are set in
a horizontal position, with the negative
feeding through a hole in the reflector, the
negative carbon should be set slightly
lower than the positive so that the positive
carbon will burn with a "cup-shaped
crater" (Fig. 28).

If the negative carbon is set too low, a
lip will be formed on the upper edge of
the positive carbon and the light will be
thrown downward, with a certain percent-
age of light being lost insofar as its value
for screen illumination is concerned (Fig.
29). If the negative carbon is set too
high, a lip will be formed on the lower
edge of the positive carbon and the light
will be thrown upward, with a resultant
loss in light on the aperture plate (Fig.
30).

In the angular type of mirror reflecting
arc lamp, that is, the type in which the
positive carbon is set in a horizontal posi-

Figure 21

tion and the negative at an angle of about
75° with the horizontal, the negative car-
bon should be set so that a square or
cup-shaped crater is formed. It is taken
for granted, of course, that both positive
and negative carbons will be in alignment,
otherwise some of the light would be de-
flected to the side of the lamphouse.

Care of Lamps

Figure 31 shows a 12m/m X 8" positive
and an 8m/m X 8" negative burned at 40
amperes. Both positive and negative car-
bons have spindled or needled excessively
due to the very heavy overload. It "will
be recalled that this trim is recommended
for 21 to 25 ampere service. The same
trim is shown in Figure 32 operated at the
specified current load. Excessive spindling,
however, is not always due to overload, for
it may be caused as readily by lack of
sufficient pressure on the carbon in the
holder. It may also be caused by the car-
bons being clamped too far away from the
burning points, thus necessitating the car-
bons carrying the current load their en-
tire lengths.

Of all the projection lamps on the mar-
ket today the mirror or reflecting arc type
is the most sensitive to draughts of air
passing through the lamphouse. This is
due to the fact that the current employed
is considerably less than that used in any
of the other types, resulting in the emission
of a comparatively weak arc stream. Ex-
treme care should foe taken to have the
ventilating system on the lamp so regu-
lated'that the exhaust fan, when in opera-
tion, will not extinguish the arc.

High Intensity Lamps

Short life of high intensity positive pro-
jector carbons may result if the positive
carbon is set too far forward. As slight

SP^^ JfffHwf

igure 31

ttwtMWttnwMiMiiiiiiii 1 1_ tfkffij

-m

a protrusion as %" beyond the proper
point will decrease the life, we have found,
about ten per cent.

Corrosion Troubles

Now and then someone complains about
the Orotip negative projector carbons
spindling in high intensity lamps. In thd
H & C and Sunlight lamps the V-shaped
rest (as it is commonly referred to) caf-
ries a certain percentage of the current.
In order to function efficiently this rest
must be kept perfectly clean so that a
good contact is assured. Many projec-
tionists consider it worth while to chip
out any corrosion, which might have
formed, after every reel. In other cases,
this corrosion is allowed to remain until
such time as very little current is passing
through the V rest, consequently, all of
the current is obliged to flow through the
lower clamp or holder with the result that
the entire carbon is carrying the load.
Being of very small diameter, it breaks
down under this load and the carbon
"spindles" or "needles" excessively.

Frequently the spring which controls
the tension between the negative carbon
and the V-shaped rest loses its temper, and
as a result the carbon arcs at the V rest
and spindles excessively. In some types
of lamps a weight is used instead of a
spring. It is good practice to test the
tension between the . carbon and the rest
after each reel.

Meter Checking

Another operating fault which is com-
mon, not only to high intensity lamps, but
to all lamps, as well, is the overloading
of ca'bohs. "Carbons, like other manufac-
tured articles, have physical limitations.
If a' carbon designed for 100 amperes is
burned at 130 amperes, the natural result
is • short life and spindling. If carbons

Figure 29

Figure 32

Figure 30

are : spindling, the first move should be to
check the amount of current drawn at the
arc.

It frequently happens that the wall am-
meters have not been calibrated since they
were installed, and as a result are not
reading correctly. This is no reflection
whatever on the make or type ot am-
meter in use as ammeters are very sensi-
tive and consequently require attention
from time to time. We have found am-
meters off as much as 20 amperes. If
your ammeter has not been checked for
some time, our suggestion would be that
you have the power company supplying
your current check the current at the arc
for you.

{Conclusion)

The Motion Picture Projectionist

November, 1929

Vacuum Tube Test for Western Electric Sound

Projector System

The following- instructions for tube testing were compiled by

R. H. McCullough, Supervisor of Projection for Fox

West Coast Theatres, and were incorporated in a

bulletin on the subject which was sent to all

units of that theatre chain. The instructions

>£ are concise and thoroughly cover the

subject of tube testing, thus making

a valuable addition to every

projectionist's store of

information.

THESE instructions are outlined for
the purpose of standardizing the
tube tests made on Western Electric
sound projector systems. Any tube failing
to meet the following requirements will be
considered as unsatisfactory for use. All
tubes, with the exception of KS-6243 ex-
citing lamps, will be replaced free if they
fail to meet these requirements before they
have given a useful service for 100 hours.

239-A Tubes

These tubes shall be tested in the first
socket of the 41-A Amplifier. In case the
installation is of the older type, where the
41-A Amplifier is not included, the tubes
should be removed from the theatre and
taken to a theatre where a 41-A Ampli-
fier is installed,
(a) Adjust all currents and voltages of
the system to their normal operating
values.
■(b) Place the tube to be tested in the
first socket of the 41-A Amplifier.
•(c) Vary the filament current, between
the limits of .220 amps, to .270 amps.
•(d) While varying the filament current,
as noted under (c), hold the plate
current button of tube number one
in.
■(e) During the above operation, the plate
current, as noted on the plate current
milliameter, shall not vary beyond
the limits of 1.3-5, 1.6-5 milliamperes.
{f) Any tube falling outside the limits
specified under (e) shall be consid-
ered as defective.
<g) Adjust the filament current to .270
amps with all tubes in position in the
41-A Amplifier.
(h) Note the plate current reading of
tube number one, by operating the
proper push-button. Remove this
tube and the tube in socket number
two ; place number two tube in socket
number one, and tube number one in
socket number two; operate the push-
button of socket number one and ob-
serve the plate current value of this
tube. Similarly interchange tubes
two and three, and observe the plate
current of tube number three in
socket number one. In other words,
observe the plate current values of
all tubes in socket number one, while
holding the filament current at .270
amps.

(i) Use the tubes as follows: —

1. Tube with highest plate current value
noted when making test (h) to be
used in socket number three.

2. Tube with next highest plate current
to be used in socket number one.

3. Tube with lowest plate current value
to be used in socket number two.
NOTE: It is to be understood that
the tubes referred to in paragraph (h)
and (i) must first have tested satis-
factorily under the tests outlined in
paragraphs (a) to (f) inclusive.

205-D Tubes

All 205-D tubes shall be tested in the
first socket of the amplifier position of the
42-A Amplifier or in the third socket of
the 8-B Amplifier. This includes the 205-
D tubes used in the motor control boxes.
Proceed with the test as follows : —

42- A .Amplifier Test.

(a) Place the tube, to be tested, in socket
number one in the amplifier position
of the 42-A Amplifier.

(b) Adjust all voltages and currents of
the system to their normal values.

(d) The indicated plate current value of
the remaining tube under test shall
be between the limits of 25-45 milli-
amperes.

Tube Balance.

It is important that the two rectifier
tubes and amplifier tubes be balanced.
Proceed with balancing test as fol-
lows : —

Equip the 42-A Amplifier with four
tubes, which have complied with the
requirements as specified under para-
graphs (a) to (d) inclusive.

(e) Remove one of the amplifier tubes
and observe the plate current value.
Replace this amplifier tube and re-
move the remaining one. Observe
the plate current value. The two
values of plate current should be
within 5 milliamperes of each other.
If they are not within 5 milliamperes
of each other, select a tube from the
spare supply which will give an in-
dicated value within the limits. In
other words, the amplifier tubes when

By R. H. McCULLOUGH

tested individually must match each
other within the limits of 5 milliam-
peres. In cases where it is necessary
to remove a tube from the amplifier,
because of difficulty in obtaining
proper balance, the tube should be
labeled with the indicated plate cur-
rent value and placed in the spare
parts cabinet. If the tube is labeled,
it will minimize the labor of re-test-
ing when selecting a tube for balance
at some future date.

(f) 205-D Tubes which are used as rec-
tifiers, shall be balanced as noted
under paragraph (e).

(g) It is to be understood that a balanced
pair of rectifier tubes must, when
used in combination with a pair of
amplifier tubes, give a combined
plate current reading within the red
limits inscribed on the face of the
plate current milliameter.

8-B Amplifier Test.

In testing 205-D tubes in the 8-B Am-
plifier, proceed as follows :

(a) Adjust all currents and voltages of
the system to the normal values.

(b) Insert tube to be tested in the third
socket of the 8-B Amplifier.

(c) Insert the plugs of the 514-A meter
panel in the proper jacks for read-
ing the filament and plate currents
of the third-stage tube in the 8-B
Amplifier.

(d) Vary the filament current of the tube
under test from 1.4 to 1.6 amperes.

(e) While making the variation noted
under (d), observe the plate current

values of the tube under test.

(f) If the plate current values noted vary
outside the limits of 16 to 28 milli-
amperes, the tube is not satisfactory
for use.

102-D, E. F. & G. Tubes

The above tubes shall be tested in the
first socket of the 8-B Amplifier. Proceed
with the test as follows : —

(a) Adjust all voltages and currents of
the system to normal values.

(b) Insert the tube, to be tested, in the
first socket of the 8-B Amplifier.

(c) Insert the plugs of 514-A Meter
panel in the proper jacks for reading
the plate and filament currents of
the first tube in the 8-B Amplifier.
Adjust the filament current to .97
amperes and observe the plate cur-
rent value, which shall be within the
limits of .0005 to .001 amperes.

(d) Vary the filament current from .97
amperes to .90 amperes and observe
the plate current.

(e) Varying operation, the plate current
shall not vary more than .00015 am-
peres.

211-E Tubes
These tubes shall be tested in either the

November, 1929

The Motion Picture Projectionist

43-A or 10-A Amplifiers. Proceed with
the test as follows : —
Filament suspension spring test.

The filament in the 211-E Vacuum Tube
is held tight by compression spring sup-
ports located on top of the insulating block,
which are located at the extreme upper end
of the tube element assembly. The pur-
pose of these springs is to compensate for
changes in filament length, which occur
due to variations in filament temperature.
In case the springs do not function prop-
erly, they will permit the filament to sag
and come in contact with the grid result-
ing in a short circuit in the filament and
grid. In case this occurs, the 43-A Am-
plifier Power Supply Transformer will be
burned out. In order to guard against
this, before placing a new tube in service,
proceed with the following test.
(a) Make sure that all current supplies

to the system are disconnected,
(to) While observing the suspension
springs with the aid of a magnifying
glass, apply the normal filament cur-
rent only, to the tube under test. As
the filament becomes heated, there
•should be a perceptible upward move-
ment of the suspension springs.

(c) After the filament has attained nor-
mal operating temperature, discon-
nect the current supply. As the fila-
ment cools off there should be a
noticeable downward movement of
the suspension springs.

(d) In case no movement can be noted,
as outlined under paragraphs (b)
and (c), the tubes shall be rejected.

Filament Emission and Balance Test

43-A Amplifier Method.

(a) Place the tube, to be tested, in socket
number one in the amplifier position
of the 43-A Amplifier.

(b) Adjust all voltages and currents of
the system to their normal values.

(d) The indicated plate current value of
the remaining tube under test shall
be between the limits of 50-115 mil-
liamperes.

Tube Balance.

It is important that the two rectifier and
amplifier tubes be balanced. Equip the
43-A Amplifier with four tubes, which have
complied with the requirements as specified
under paragraphs (a) to (d) inclusive.

(e) Remove one of the amplifier tubes
and observe the plate current value.
Replace this amplifier tube and re-
move the remaining one. Observe
the plate current value. The two ob-
served values of plate current should
be within 10 milliamperes of each
other. If they are not within 10 mil-
liamperes of each other, select a tube
from^ the spare supply, which will
give an indicated value within the re-
quired limits. In other words, the
amplifier tubes, when tested individ-
ually, must match each other within
the limits of 10 milliamperes. In
cases where it is necessary to remove

a tube from the amplifier, because of
difficulty in obtaining proper balance,
the tube should be labeled within the

indicated plate current value and
placed in the spare parts cabinet. If
this suggestion is carried out, it will
minimize the labor of re-testing when
selecting a tube for balance at some
future date.

(f) 211-E Tubes, which are used as recti-
fiers shall be balanced as noted under
paragraph (c).

10-^4 Amplifier Method.

(h) Place the tubes, to be tested, in the
sockets of the 10-A Amplifier.

(i) Adjust voltages and currents of the
system to normal.

(j) Reduce the filament voltage of the
10-A Amplifier tubes to 5 volts.

(k) Remove one tube from each side of
the amplifier.

(1) Adjust the filament voltage of the
amplifier to 10 volts.

(m) Remove one tube from the amplifier
and note the plate current reading of
the remaining tube, which should be
within the limits of from 40 to 100
milliamperes.

(n) Replace the tube just removed and
remove the tube just tested, and ob-
serve the plate current value. The
two tubes should test within 10 mil-
liamperes of each other.

(o) Remove the two tubes just tested and
insert the first tw$ tubes originally
removed as specified under operation
(k). Test these two tubes, as out-
lined under operations (1) to (n).

(p) Care should be taken to run off the
plate supply to the tubes when re-
moving or replacing them in a socket.
Otherwise, there is danger of caus-
ing a high voltage flash over. In
performing operation (o), care must
be taken to warm up the two cold
tubes, which are placed in the ampli-
fier for test.

(q) When the Amplifier is equipped with
four tubes, meeting the requirements
as outlined above, and all voltages

and currents adjusted to normal, a
current reading on the 10-A Ampli-
fier milliameter shall be obtained;
the value of which shall be within
175 to 250 milliamperes.

219-D Tubes

A 219-D Tube shall be considered as sat-
isfactory, as long as it will supply normaS
voltage to the remaining tubes in the sys-
tem when all remaining tubes in the system*
are satisfactory. When a pair of 219-D
tubes become badly out of balance, there
will be a perceptible hum and vibration
present in the 6000-A rectifier.

An indication of low filament emission
is a noticeable increase in the operating
temperature of the tube. Usually the plate
of a tube, which has low filament emission
will become very red as compared with the
plate of a normal 219-D tube. Any tube,
which shows signs of becoming white hot,
should be removed from the rectifier as
there is danger of the plate melting down
and causing damage to the supply trans-
former.

KS-6243 Exciting Lamps

The lamps are not satisfactory for use
when a perceptible film of tungsten vapor
has accumulated on the inner surface of
the glass bulb between the filament and
the end of the lens tube. It is permissible
to operate a lamp, which has become black-
ened at the upper end, providing the glass
surface, between the filament and the end
of the lens tube, permits unobstructed pass-
age of the light.

It is necessary that each projectionist,
upon installing tubes in the amplifiers and
control boxes, label each tube with a small
sticker, marking date and time installed, so
that each projectionist may keep check on
tubes to see if they have given 100 hours'
service without deterioration. Any tube,
which does not give 100 hours' service, will
be replaced free of charge.

It is well to note that operating an am-
plifier with flat tubes will eliminate high
frequency and cause considerable distortion.
It is to your advantage, as well as to the
theatre's advantage, to see that the sound
in theatres is 100 per cent perfect in order
to avoid severe criticism.

S. M. P. E. Abstracts

THE following abstracts from papers
which were presented at the Fall
Meeting of the Society of Motion Picture
Engineers, in session at Toronto, Canada,
October 7 to 10, are particularly interest-
ing to projectionists. W. B. Rayton,
Bausch & Lomb Optical Co. technician, of-
fered a paper titled "The Optical Problems
of Wide Film Motion Pictures," from
which the following abstract is taken :
The motion picture industry seems to
be about to adopt film wider than the
standard 35 mm. film now in universal
use. Such a step imposes very grave
burdens on the optical systems required
for photography and projection. Both
in photography and in projection,
lenses have been called for which,
while maintaining the high speed and

fine definition necessary for the condi-
tions in the studios and theatres, must
cover hitherto unrealized fields of view.
In projection, the question of illumi-
nation bristles with difficulties.

New Wide Film Lens

The Bausch and Lomb Optical Com-
pany has been cooperating with the
sponsors of wide film motion pictures
by designing the new lenses involved.
New photographic lenses which cover
a picture area 23x46 mm. at a speed
of f :2.3 in focal lengths as short as
50 mm; new projection lenses which
will project, with beautiful definition,
pictures of this size in focal lengths as
short as 3 inches ; and new condensers
to bring the brightness of the projected

The Motion Picture Projectionist

November, 1929

picture up to a satisfactory- level have
been perfected.

Another phase of wide film ;was treated
in the paper "Some Practical Aspects and
Recommendations on Wide Film Stand-
ards," by Messrs. A. S. Howell and J. A.
Dubray. This paper is divided into three
parts, the first taking into consideration
the psychological and artistic factors
which suggest the recommendation of a
change from the present standard in the
form and dimensions of the film, the sec-
ond containing suggestions for film dimen-
sions, and the third dealing with the me-
chanical alterations necessary to a general
introduction of wide film in the industry.
An abstract of this paper follows :

The paper is divided into three parts,
the first taking into consideration the
psychological and artistic factors which
suggest the recommendation of a
change from the present standard in
the form and dimensions of the motion
picture frame. The recommended frame
shape is that of a rectangle whose sides
are in the ratio of 3 to 5.

Film Dimensions

In the second part of the paper, the
authors suggest three film dimensions
which are respectively called the "Eco-
nomic Ideal," the "Spectacular," and the
"Extreme," which differentiate from
each other in their picture area and in

the length and width of the sound rec-
ord, which is assumed to be printed on
the same film as the picture record.

The problems involved in the adoption
of any of the three dimensions are an-
alyzed in regard to size, shape and posi-
tion of the perforations, also in regard
to the possible influence that the larger-
size film would have on sound recording.
A brief discussion is presented on the
engineering developments which would
be necessitated by the adoption of the
new standards in regard to film shrink-
age; and the problems that are involved
by their adoption in regard to the photo-
graphic and projection optical system
are considered.

Urge Standardization

The third part of the paper deals with
the mechanical alterations that the adop-
tion of the new standards would bring
forth, with due consideration of the
economical factors involved.

The paper concludes by suggesting the
formation of a special standing commit-
tee, which should include representative
members of all branches of the motion
picture industry, and which should be
given power and authority to discuss
and take definite decisions in regard to
the creation and adoption of new dimen-
sional standards.

Electrical Measuring Instruments

ELECTRICAL meeasuring instruments
should be handled carefully and not
subjected to any jars or hammering. Port-
able instruments are often placed in posi-
tions where they are subjected to a strong-
magnetic field or to high temperatures.
Both of these cause errors in the reading.

In the permanent magnet type of direct
current instruments, if the temperature is
increased the strength of the magnets will
be decreased which tends to decrease the
reading of the instruments, but at the same
time the strength of the holding spring will
be decreased and these two errors tend to
neutralize each other. As a general rule,
however, these meters will read low when
they are hot.

In the ammeters of this type with an in-
ternal shunt, the heat from the shunt will
usually cause the instrument to read low.
Up to about 25 amperes these meters read
correctly, but above that they should not
be left in the circuit at all times. Direct
current meters for reading' large currents
should be provided with an outside shunt.

Shielding Meters

Errors will be caused by stray magnetic
fields, the size depending upon the strength
eft the field. An alternating current field,
if weak, will not affect a direct currait
meter, but if strong it will exert a de-
magnetizing effect upon the meter and
cause a low reading. These fields may be
caused by any electric generator or motor,
a conductor carrying current, or by other
meters. Switchboard meters should be
shielded from the effect of these fields by
an iron case.

Other causes* of errors which may be
mentioned are the friction of pivots, de-
fective springs and lack of balance of
moving parts. These faults, however, should
not be found in well-made meters.

For measuring A. C, current transform-
ers and not shunts should be used. Care-
should be taken that no more meters are
connected on the secondary of the trans-
former than the number which it is
designed to carry. At light loads the ratio
of transformation is not accurate and small
errors will be introduced. The secondary
of 'both current and potential instrument
transformers on high potential lines should
be grounded. This not only protects the
operator but prevents errors due to static
electricity.

Meter Inspection

In the A. C. induction meters the error
due to small changes in frequency should
be slight. Rattling and humming of meters
is caused by loose parts. In the D. C.
wattmeters the case may become perma-
nently magnetized and affect the reading.

Wattmeters should be inspected at least
once a year when they should be thor-
oughly cleaned and the pivot at the bottom
oiled. The creeping of wattmeters is usu-
ally due to vibration of the wall on which
they are fastened. The potential coil is
connected to the line at all times and this
in connection with the starting coil gives
a small torque. Another cause is the con-
nection of a meter on a higher voltage than
that for which it is adjusted. A good watt-
meter should give accurate readings on
both light and heavy loads under a wide

variation of power factor, frequency and
wave form. The damping magnets should
not lose their magnetism and the case
should be moisture, bug and dust proof.

Good electrical contact is extremely im-
portant with all measuring instruments.
This is particularly important in the low
reading milli-voltmeters when used for
measuring current with external shunt. If
the resistance of the meter is only a few
ohms, a corroded or dirty terminal may in
troduce a large percentage of error.

Voltmeter Testing

The voltmeter is merely a galvanometer
of high resistance connected across two
conductors of opposite polarity. The re-
sistance of the voltmeter is extremely high
in comparison with that of the conductors,
and but a minute current flows through it.
As this resistance is fixed the only way to
vary the current flow is to vary the elec-
tromotive force.

An increased electromotive force will in-
crease the current flow and likewise a de-
crease of one will decrease the other. And
these current variations produce corres-
ponding deflections of the needle. The de-
flections show actually the changes of
electromotive force. The scale divisions
are calibrated or given a value in volts
either by using electromotive forces of
known value or by means of a standard
voltmeter.

Tests with a Voltmeter

The voltmeter is used for a wide range
of tests. On electrical machinery the volt-
meter is used for ground tests, insulation
tests, resistance tests, short-circuit tests,
open coil tests. The inside electrical
worker uses a voltmeter for circuit ground
testing in conduit circuits,, metal moulding
circuits, armored cable circuits, etc.

The Ohmmeter

The ohmmeter is a very practical instru-
ment for accurately recording the resist-
ance of a coil or circuit for which the re-
sistance in ohms is desired. The ohmmeter
operates in a manner somewhat similar to
a wheatstone 'bridge. The ohmmeter will
do a similar range of work as done by
the bridge and it costs one-half the price.
In everyday practice the ohmmeter is used
for all sorts of electric current and elec-
tric heating circuit resistance tests. A
wide range of tests in radio manufactur-
ing is covered using an ohmmeter.

Film Fire Statistics

Seventy-one per cent of all theater fires
originate in the projection room while ma-
chines are in operation, causing hundreds
of fires annually and resulting in a yearly
loss of approximately $3,000,000 to theatre
properties and equipment. Losses sustained
from destroyed film in theatre fires, which
are not included in, the $3,000,000 total,
would send this figure considerably higher.

Theatres suffered an $18,000,000 loss
during the five years from 1922 to 1926,
inclusive, with the average for recent pe-
riods being lower, due, principally, to the
many new devices and types of equipment
now being built to eliminate fire hazards. —
The Film Daily.

November, 1929

The Motion Picture Projectionist

Color Film Processes

By Emery Huse

Motion Picture Film Dept., Eastman Kodak Company

A YEAR ago the motion picture in-
dustry generally, and Hollywood
particularly, was just entering seri-
ously the field in sound photography. At
the present moment color photography, or
rather the anticipation of it, is in the minds
of all motion picture producers. It is the
desire of the author of this article to call
to the attention of those interested in the
general subject of color some of the under-
Tying physical facts of color photography
together with a historical resume of what
has been done in this field.

One must first go back appreciably and
review somewhat some of the fundamental
facts in the study of light. From the
physicist's point of view, the study of light
is a study of activity which originates in
luminous bodies and causes the sensation of
vision when it enters the eyes. There are
two distinct phases in the study of light:
first, quantity, which deals with differences
in brightness and, second, quality differ-
ences are classified under the phenomena
of color.

Newton's Contribution

Sir Isaac Newton made many advances
in the study of light and his many ex-
periments led him to believe in a certain
hypothesis. Newton was the first to get a
clear idea of color, which idea he attained
through a study of glass prisms. He was
the chief advocate of the corpuscular theory
which maintained that light consisted of
very minute weightless material particles.
It is rather a strain on the imagination to
think of material corpuscles flying with
enormous speed through a solid substance
like glass with so little hindrance as glass
seems to offer to the passage of light. It is
also somewhat difficult to explain the phe-
nomena of reflection and refraction under
this theory. Color was accounted for by
differences in size and shape or in some
other characteristics among the corpuscles.

The newer, and at present accepted,
theory considers light as made up of waves
acting in much the same way as waves pro-
duced by disturbances in a body of water.
Under this theory there is little difficulty
in explaining reflection and refraction.
Furthermore, color is accounted for very
simply by the supposition that differences
in color correspond to differences in the
length of the waves. The medium in which
these waves act is termed "ether," which
means that empty space has properties
other than mere extension; properties that
enable disturbances carrying energy to pass
through, the passage requiring finite time.
We know that light travels at a rate of ap-
proximately 186,000 miles per second.

Theories of Color Vision

Prior to actual work on the recording of
color photography, it is necessary to con-
sider somewhat the theories of color vision.

'International Photographer.

One, that of Young and Helmholtz, is a
purely physical theory, while another, that
of Hering, is psychological. These two
theories are given considerable weight. The
Young-Helmholtz theory considers that the
retina consists of three distinct sets of
nerve fibers, each giving a single sensa-
tion, one set a red sensation, another a
green, and the third a blue-violet sensa-
tion.

The Hering theory deals with three pri-
mary sensations and postulates certain con-
trasts caused by chemical changes under the
influence of light in three hypothetical
fluids.

Our present existing knowledge teaches
us that there are three primary colors, and
these three colors are blue, green and red.
Newton at one time advanced the theory
that there were seven primaries. However,
based upon work by physicists and psy-
chologists, it is pretty well established that
blue, green, and red are considered univer-
sally as the three primaries.

Color Photography

Three-color photography is based on the
fact first discovered by Clerk Maxwell
about 1860 that all colors can be matched
by a mixture of the three primary colors,
red, blue, and green, if the proportion of
these constituent colors be rightly chosen.
The work of Maxwell was based on the
discovery by Young in 1807 that all color
perception is the result of three funda-
mental color sensations singly or in various,
combinations and proportions, and it is
safe to say that the work of Maxwell is
the foundation upon which three-color
process of natural color-photography is
based.

Prior to Maxwell's time such men as
Seebeck, Becquerel and Daquerre did quite
a little experimental work on the reproduc-
tion of color, but they were handicapped by
the fact that they could give only a partial
reproduction and had no way to fix their
images.

Workers in the Art

Later on, natural color photography
necessitated the use of a light sensitive dye
which dye faded out to a colorless sub-
stance. A dye is decomposed only by the
light which it absorbs, which color is com-
plementary to its own color. Certain ani-
line dyes bleach comparatively rapidly in
light, hence after three such dyes are
chosen so as to form the three fundamental
colors, red, green and blue-violet, and these
are coated on a white surface such as paper
in three separate layers and the whole ex-
posed to a colored object, in red light, the
blue and green dyes are bleached out, leav-
ing the red. In the same way in blue light,
blue will be left as red and green are
bleached out, and in the case of green, red
and blue are bleached out, while the colors
which are mixtures of these each will be

bleached in direct proportion to the amount
of the fundamental colors present.

Processes based on this principle were
conceived by such men as Cros in 1861,
Leisegand in 1889, Ives in 1891, and others
up until 1910.

Despite the apparent simplicity of the
process, it has never furnished a satisfac-
tory solution to the problem of natural
color photography. It was difficult to se-
cure three dyes having the proper color
and of identical light sensitiveness, and it
was further difficult to prevent further
bleaching of the dye after exposure.

In 1897, Prof. Lippman, of Paris, de-
vised an ingenious process of color
photography dependent upon the prin-
ciple of light interference. Lippman's
method was to expose a specially prepared
fine-grained transparent emulsion of silver
chloride in contact with a bath of mercury
which reflected back into the emulsion the
waves of light which reached it, thus set-
ting up in the sensitive film the phenomena
of interference. This process, however,
although extremely interesting, was little
more than a laboratory experiment from
the standpoint of producing photography
in natural color.

This brings us back to the time of Max-
well, who, as previously stated, did the
basic work on the principle of three-color
photography.

The Additive Process

In natural color photography there are
two very general classifications, the addi-
tive and subtractive processes. As a gen-
eral statement the additive process of color
photography can be summed up in the
statement that we start with a colored
light from which we produce white by ad-
dition. In other words, we take red, green
and blue and by an additive method pro-
duce a white light. Photographically, this
process may be analyzed as follows :

The color sensation negative records by
density the presence of that particular color
in the subject, i. e., the red sensation nega-
tive records the red of the subject in terms
of greater or lesser density, according to
the amount of red present in the various
portions of the subject. A positive trans-
parency from this negative will reproduce
the red sensation by means of its clearer
parts. The parts of the subject containing
the purest red will be represented by clear
glass, those parts with some red by a
medium density, while those parts contain-
ing no red whatever will be of maximum
density. Now if this transparency is
viewed in red light it will reproduce the
red sensation of the original subject. In
a like manner the blue and green transpar-
ency will, when viewed in blue and green
light, reproduce the respective color sensa-
tions of the original subject.

The three records may now be com-
bined and the natural colors of the subject
(Continued on page 36)

The Motion Picture Projectionist

November, 1929

to fulfill

ANNOUNCING A NATION-

RCA PHOTOPHONE

RCA Photophone promised the
theatre owners:

The finest sound equipment that
men and money could devise.

2 The fairest prices compatible
with that quality.

3 Prompt and efficient service in
the maintenance of that equip-
ment.

RCA Photophone has kept its promise
to produce a superior sound system at
an equitable price. It is the world's lowest
priced, high-quality sound apparatus —
the ultimate in tone and precision.

But what is not so generally known are
the steps which RCA Photophone has
taken to provide prompt and efficient
service for its equipment.

RCA PHOTOPHONE, lime.

SUKSIIHAkY CEE HAI>IO rOKPOKAllllN Q£ AMKkMIA
4 I I FIFTH AVENUE - NEW YORK. CITY

November, 1929

The Motion Picture Projectionist

a, -promise

WIDE NET WORK OF

ERVICE STATIONS

Now this story can be told. After months
of preparation RCA Photophone an-
nounces the formation of a nation-wide
network of service stations. The first
eleven of these branches are now being
opened. Each will be in charge of a su-
pervising engineer and an assistant engi-
neer, with a corps of factory- trained
technicians as their aides. These experts
are your assurance of a satisfactory per-
formance'

RCA Photophone wants satisfied custom-
ers. It will go to any length to insure
their satisfaction. To this end, RCA
Photophone will spend more than a mil-
lion dollars a year to carry out its ever-
expanding program of service to the
exhibitor — a program that considers only
the results — not the cost.

RCA Photophone service stations will
cover the country. The initial stations to
be opened include New York, Boston,
Philadelphia, Atlanta, Pittsburgh, Cleve-
land, Chicago, Kansas City, Denver, San
Francisco and Seattle. Others will be
opened as rapidly as occasion demands.

The Motion Picture Projectionist

November, 1929

I 1,000

to fulfill

ANNOUNCING A NATOKvJ

RCA PHOTOPHONE

November, 1929

The Motion Picture Projectionist

OOO

«£ -p&omisel

WIDE NET WORK OF

SERVICE STATIONS

RCA Photoplione promised the
theatre owners:

\ The finest sound equipment tJtat
men and money could devise.

2 Tlie fairest prices compatible
with that quality.

3 Prompt and efficient service in
the maintenance of that equip-
ment.

RCA Photophone has kept its promise
to produce a superior sound system at
aD equitable price. It is the world's lowest
priced, high-quality sound apparatus—
the ultimate, in tone and precision.

But what is not so generally known are
the steps which RCA Photophone has
taken to provide prompt and efficient
service for its equipment.

Now this slory can he told. After months
of preparation RCA Photophone an-
nounces the (<>[ million of n nationwide
network of service stations. The first
eleven of these branches are now being
opened. Each will he in elmrge of a su-
pervising engineer and an assistant engi-
neer, with a corps of factory-trained
technicians as their aides. These experts
are your assurance of a satisfactory per-
formance

It Gil. PHOTOPHONE, Inc.

tnn'OKAtiUM ot- amlhtts

RCA Pholopfa

the country. The initial stations to
be opened in. -In. I. New York, Boston,
Philadelphia, Atlanta, Pittsburgh, CIi
land, Chicago, Kansas City, De
Francisco and Seattle. Others will bo
opened as rapidly ;i- occasion demands.

The Motion Picture Projectionist

November, 1929

Equipment Troubles and Maintenance

By C. R. TRAVIS

THE majority of sound projection
equipment manufacturers are en-
deavoring to give the theatre
owner as much service as possible in the
matter of maintaining the efficiency of the
apparatus which he has purchased from
them. One of the best ways in which to
render this service to the exhibitor is to
place at the disposal of his projectionist
who daily handles the equipment every
opportunity and facility for learning the
details of the system. Co-operation with
the projectionist in this respect is one of
the most important functions of any mer-
chandising plan for sound equipment, and
I speak now from experience in just such
a capacity.

In the last analysis it is the projectionist
to whom the exhibitor looks for results
obtained with any given equipment. Lack-
ing the technical knowledge to enable him
to accurately judge the worth of an
equipment, the exhibitor must necessarily
place full trust in his projectionist. Sound
equipment manufacturers recognize the
projectionist's responsibility in this respect
and they are therefore ever on the alert
to see that his wishes with respect to the
equipment are carried out. It is undoubt-
edly true that in the past a cloak of secrecy
was thrown about certain parts of sound
systems, yet in the light of past experiences
in the development of any new art, this
condition is entirely understandable.

Observe Servicing

In the case of the larger companies
regular service inspections assist the pro-
jectionist in maintaining the efficiency of
his equipment; but with the smaller dis-
tributors the burden of maintenance and
"trouble shooting" is usually transferred
to the projectionist.

Trouble-shooting is not a haphazard
procedure. To be successful it must be
rapid and well-ordered, and the few simple
tests necessary must be made thoroughly
and a definite "yes" or "no" received foe-
fore proceeding with the next step. The
piojectionist by every consideration is en-
titled to know as much as possible about
the equipment he is called upon to operate.
A goal time to obtain much useful infor-
mation is' while the engineer is making the
installation, for during this period many
of the common troubles of the system will
show up. Lacking this opportunity, the
projectionist should observe closely the
work of the service man on his periodic
visits.

Essentials All Alike

Essentially all sound reproducing sys-
tems are alike. They may differ in ex-
ternal appearance, in size and shape, in
the amount of space they occupy, and in
the quality of delivered results, yet they
all are substantially the same. They all
have been designed to do the following
work : — change mechanically or photo-
graphically-recorded sound into electrical
energy, supply a means for controlling the
amount of energy passing a certain point,

a means for amplifying this energy to
requisite levels, and a means for changing
this amplified energy into sound.

The conventional designations for the
equipment performing these four opera-
tions are as follows : In the reproduction
of wax records the term "pick-up" or "re-
producer" is most commonly used. In
film reproduction the usual terms employed
are "film reproducer," "sound head," and
"film attachment." The means for con-
trolling the electrical energy passing a
certain point is known as the 'fader." A
key or switch provides the means for con-
necting the fader to either the film or
disc attachments of the projector.

The amplifier performs the function of
building up the electrical energy to the
required level. The horns or loudspeakers
transform the electrical energy into sound.
In future issues of this publication, each
of these units with their common troubles
will be covered in detail. In this install-
ment we shall discuss methods of tracing
one of the major troubles of any system.

"No Sound" Common Trouble

"No Sound" is of course the most com-
mon trouble. To one who is familiar with
his equipment this trouble should offer
little difficulty. We should remember that
the entire apparatus does not suddenly
cease functioning, and it is rare indeed that
more than one trouble develops at one
time. "No sound" is always due to the
breaking of some particular unit in the
complete circuit.

Let us assume first that all keys,
switches and other accessories are in their
correct operating positions. A few seconds
should suffice to check up on this point.
One of the first impulses of most projec-
tionists when the equipment "goes dead"
is to run to the amplifier panel, but in
nine cases out of ten they fail to locate
the trouble there. The amplifier is to be
checked, of course, but when trouble oc-
curs, start at the beginning — either at the
sound head or at the disc pick-up, depend-
ing on whether you are running sound-on-

filrn or discs. After checking your con-
nections, photo electric cell, exciter lamp,
etc., then proceed to check the equipment
step by step to the amplifier.

In Figure 1 there are shown connec-
tions in a general circuit which should be
remembered before any trouble hunting be-
comes necessary. This diagram shows
that about the closest point one can get to
the electrical center of the system is at
the input to the amplifier. If one can de-
termine whether or not energy is reaching
this point, one can definitely isolate the
trouble into a certain section of the
equipment.

Amplifier Input Check

Let us say we find that energy is being
received at the input to the amplifier : —
we then may foe sure that the trouble lies
ahead of this point. If no sound is heard,
we may be sure that the trouble lies in
back of this point. A pair of head-
phones of good quality will respond to the
energy received from the reproducers at
this point — that is, with the fader at the
top step.

Another quick test for "no sound" lo-
cation to either one side or the other of
the electrical center of the system is to
tap the first tube in the amplifier with a
finger. This tap jars the tube elements
and sets up a small wave that should be
audible in the stage horns or in the pro-
jection room monitor. If the amplifier
from the first tube to the horns is working
as it should, this sound will foe heard in
the horns, and it would be logical to as-
sume that the first half of the system is in
trouble. If the ringing sound is not heard
in the horns, then one may assume that the
last half of the system is not working.

Assuming that the test indicates trouble
in the first half of the circuit, our next
task is to locate the trouble either in the
pick-up elements (disc or film), or in the
fader. The check at this point is much
the same as that at the amplifier.

Listen with a headset to the output of
the pick-ups (input to the fader), at the
(Continued on page 38)

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ovember,

1929

The Motion Picture Projectionist

Dependable

ipment

Essannay Announces Strong's New "Five-
Point" Changeover

ANEW complete multiple projection
room accessory combining in one
device five essentials which are requisite for
good projection results has been announced
by the Essannay Electric Mfg. Co. of May-
wood, Illinois. This new equipment unit is
the product of L. D. Strong, president of
the Essannay Co., whose experience as a
practical projectionist emphasized the need
for a single projector mounting which
would automatically perform all the func-
tions heretofore obtainable only in several
individual units.

That the term "five-point" which Essan-
nay has applied to this device is no mis-
nomer is indicated by the fact that the
mounting includes the following features :
(1) A noiseless changeover, (2) An eye
shield, (3) Framing light, (4) An auto-
matic fire shutter finger, and (5) A film
gate opener. The device is guaranteed to
perform all of these functions, with the
mechanical changeover and fire shutter
designed to perform their work quietly,
instantaneously and efficiently.

Rigorous Test Period

This novel Strong device has been ready
for distribution for the past two months, but
it was not placed on the market for the
reason that its maker wished to test
thoroughly whether it would perform sat-
isfactorily everything that was claimed for
it. With this end in view one of the
changeovers was installed in the State Lake
Theatre in Chicago where it was subjected
to exhaustive tests under actual operating
conditions for more than 200 consecutive

performances. This test showed that the
device was capable of delivering maximum
efficiency on all five points under even the
most severe conditions.

The accompanying illustrations show
some of the more important features of this
new Strong changeover. Figure 1 shows
the complete changeover assembly mounted
on a projector as viewed from the operat-
ing side. This keyed picture indicates the
position in the assembly of the various im-
portant units.

For example, the framing light is a 110-
volt, 21 C. P. tungsten light which, Essan-
nay claims, will enable the projectionist to
have a strong direct light trained on all

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framing operations. The switch for the
framing light is conveniently located. The
glass eyeshield is warranted not to leak
light, a condition which has long been a
source of danger for the projectionist's
eyes. Also indicated in this illustration are
the handle for opening film gate, the lever
for hand use, the changeover shutter
blades, and the holes for oiling. The fram-
ing light is ingeniously located in the as-
sembly and insures maximum lighting for
all framing work.

Figure 2 shows the changeover mounting
from the reverse side of the projector.
Indicated on this keyed illustration are the
arm for opening iilm gate, cover screw, arm
to hold fire shutter down for framing, fire
shutter lever, and conduit arrangement.

The heart of the changeover is shown in
Figure 3, which shows the operating
mechanism with the outside cover detached.

Figure 3

The precautions which have gone into the
design and manufacture of this changeover
are apparent from this view of the mechan-
ism. Special rubber bumpers are standard
thereon, insuring quiet, efficiency and long
life, while another advantage is the use of
double selenoid.

For Simplex and Motiograpb

Essannay reports a considerable demand
for this new product even before it has
been formally announced from projection-
ists who have had the opportunity of testing
several trial assemblies. With the combi-
nation of five essential projection aids in
one compact, sturdily-built and performance
guaranteed unit, Essannay anticipates much
enthusiasm about the device from projec-
tionists.

This new Strong changeover is suitable
for use with either Simplex or Motiograph
projectors. Distribution of the unit is
through all branches of the National
Theatre Supply Co. Foreign orders are
handled through Edward L. Klein, 25 West
43rd St., New York City.

NEW HOUGH HORN LIFT

The new Hough horn lift is installed
under the stage floor and is operated auto-
matically. When not in use, the horns are
thus housed under the stage floor itself.
It is contained within a ceiling height of 8
feet below the stage and has a full upward
travel of IS feet, or more, if required. It is
powered by a \y2 h. p. motor, driving a cable-
consuming drum through a ball-bearing-
steel and bronze worm gearing and oper-
ates in a dust-proof oil bath. Travel up
and down is smooth and without vibra-
tion, time required for a trip being 45
seconds. Operation is absolutely silent.

The Motion Picture Projectionist

November, 1929

e Laboratory

Sound Recording with
the Piezo Crystal

ALMOST even- conceivable means of
varying a light source has been rec-
ommended and tried as a means for re-
cording sound photographically on motion
picture films. These divers methods have
met with more or less gratifying success.
However, the "piezo effect" is one of these
methods which shows "food for thought"
to those who might desire to ascertain
the availability of the process for com-
mercial sound recording. R. V. L. Hart-
ley1 patents the use of the piezo effect for
this purpose, and we are herewith quoting
this data.

The piezo effect consists of a crystal of
Rochelle salts (sodium potassium tartrate),
held under compression by two metal
plates. If a potential is applied to the
two plates, the crystal will vary in its
physical characteristics to such an extent
as to pass light through it. The piezo
effect has other characteristics which make
it adaptable for other purposes, but since
we are not concerned with these other
properties and applications, we are not
considering them here.

In the accompanying drawing we see a
source of light, 10, is focussed througn a
lens, 11, and a Nicol's prism, 12. Adjacent
the opposite face of the Nicol prism and
arranged to receive light from same is a
Rochelle salt crystal, 13, having on op-
posite faces metallic deposits, 14, to which
are electrically connected the secondary of
a transformer, the primary of which is
connected to the output of a vacuum tube
oscillator, which latter is impressed on the
piezo crystal.

The straining of the crystal due to its
vibration causes rotation of the plane of
polarized light transmitted to it twice dur-
ing each cycle of vibration. A second
Nicol prism is arranged to receive light
transmitted through the crystal, 13, and is
adjusted so that it is crossed with respect
to the prism, 12, when the crystal, 13, is
at rest. Thus when the crystal, 13, is

1V. S. Fat. No. 1,565,566, Dec. 15, 1925.

•Conducted by SAMUEL WEIN-

vibrated, light is transmitted from the
source, 10, through the combined prisms
and crystal, and the amount of transmitted
light is dependent upon the extent of
vibration of the crystal. The beam of
varying source of light thus created is
focussed through a lens and onto the
motion picture film when it is photographed
as a variable light density.

The oscillating circuit to which the piezo
crystal is electrically connected is made to
vary by means of the microphone.

C. C. N. Y. Offers Course
in Vacuum Tube Theory

OXE of the requisites for successful
. sound picture projection work is a
thorough understanding of the theory and
practical application of vacuum tubes to
the work. In connection with this" it is
interesting to note that a course in the
"Theory and Operation of Vacuum Tubes"
is to be offered this semester at the
College of the City of New York, in New
York City. The course, which will be
under the direction of E. Gordan Taylor,
M.S., will run through 16 weeks. The
class is strictly limited in number. The
instructional work consists of two hours of
lectures and discussion and one hour of
laboratory work each week.

The course has been arranged particu-
larly for those engaged in work involving a
discharge of electricity through gases at
moderate pressure as well as for those
working with radio tubes or circuits utiliz-
ing high vacuum tubes. The greater part
of the work will be devoted to a study of
the operation and theory of the three-
element type of tube.

Subjects to Be Treated

The first part of the course will be de-
voted to a brief review of a few of the
fundamental physical laws of electricity
and magnetism, after which the subject
matter proper will be treated, including
such subjects as: (1) General theory of
ionization of gases; (2) Thermionic
emission of filaments; (3) Vacuum tubes

/4A

containing two or more electrodes ; (4)
Characteristic curves of different types of
tubes ; (5) Vacuum tubes as power or volt-
age amplifiers ; (6) Rectification of alter-
nating currents by means of vacuum tubes,
and (7) Photo electric cells.

Those desiring further information on
this course may consult Mr. Taylor in
Room 107A by appointment. Fee for the
course is $25.00. Students may register in
person, or they may mail a check or money
order for $25.50, including a library
service fee, to Walter Staub, Bursar,
College of the City of New York, 140th
St. and Convent Ave., New York City.

New Color System

The Emil Busch Co. of Rathnow,
Germany, recently demonstrated at the
great Spanish exposition in Barcelona a
new method of color motion pictures. This
new method employs an optical system
which splits up the image into two small

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images, and so photographs them alongside
each other on the same film. Two color
filters — blue-green and orange-red — are
used in the process.

When the positive is run through the
projector these two color filters are used,
and an optical system is also employed by
means of which the two projected images
appear as one on the screen. The demon-
stration of this process attracted a great
deal of attention at the Barcelona exposi-
tion. Its sponsors state that the system
will have the benefit of extensive pro-
motion on the Continent.

In the accompanying illustrations, Figure
1 shows the conventional motion picture
film with the figure thereon, as is the case
with ordinary black and white; while
Figure 2 shows the same image reduced
and taken through the color filters.

Diagrammatic outline of method of
recording with the Piezo Crystal.

Eugene A. Lauste

MANY readers have requested that
we outline the work of Eugene A.
Lauste. whose name continually crops up
in discussions of development work in the

November, 1929

The Motion Picture Projectionist

Lauste's compressed air loudspeaker,
which was operated directly by a light
sensitive cell without the aid of an inter-
mediate amplifier.

sound picture art. Prior to his efforts
in the recording and reproduction of sound,
Lauste had many important contribu-
tions to motion picture technology in
the form of projectors which at that time
were examples of fine mechanical endeavor.
Reference to the accompanying photograph
of the Lauste projector will serve to con-
vey to the reader the type of work done
by Lauste.

It is in the sound picture field, however,
that Lauste did his finest work. Lauste's
British patent of 1906 was the first ever
to be issued for a means of recording
sound and scene simultaneously on film. It
will be remembered that Ernst Ruhmer

was the first actually to have disclosed a
means for photographically recording sound
and reproducing same by means of a light
sensitive cell. Lauste used the "mechan-
ical slit" for confining the variable light
source in the "sound gate," as compared
with the "optical slit" first used by
Ruhmer.

Lauste's Film Loop

Lauste was born in France but emig-
rated tc America at an early age. He
entered the laboratory of Thomas A.
Edison where he was assigned to motion
picture work. Here he designed many
mechanical movements for intermittently
advancing the film. To him belongs the
credit for the loop in the camera and
projector. Lauste was the first to demon-
strate motion pictures at the Vatican in
Rome.

It is interesting to note that it was
Lauste's testimony which influenced the
court to issue the now famous order which
dissolved the vicious patent combine which
for a time early in this century threatened
to destroy American development of mo-
tion pictures.

The records show that Lauste was active
in sound picture work as far back as
1896, when he began his experiments to
photograph both sound and scene simul-
taneously on film. It was not until 1906
that a patent covering the means for suc-
cessfully accomplishing this work was
granted to him.

Use of Diode Tube

Lauste made use of every then known
physical means for recording sound.
Among the methods employed by him were
manomatric flame, oscillating arc, shutters,
mirrors, gas-filled tubes, and string gal-
vanometers. By means of this latter device
he became the first to actually record sound

"String" galvanometer used in making the
"saw tooth" sound film record.

by what is now known as the "saw tooth"
method.

If one were to read carefully the 1906
British patent granted to Lauste, one would
note on page 5 therein reference to the use
of an "electric lamp in connection with the
loudspeaker as a means for amplifying."
No details are given as to this "amplify-
ing lamp," but the writer feels reasonably
sure that it was a "diode" tube (two-
element, i.e., a hot filament and plate),
similar to the rectifier tubes now in corn-

Showing the projector head assembly made by Lauste. The top lamp

is for the film, while the lower lamp is for the sound gate proper. Used

by Lauste for public demonstrations in 1912.

Back view of the Lauste projector. Film gate on top;

the sound gate at bottom is in the form of an adjustable

slit, for experimental work.

The Motion Picture Projectionist

November, 1929

mon use. This diode tube was in common
use by radio experimenters prior to 1906.
For some reason unknown to the writer,
this means of amplifying was subsequently
dropped by . Lauste in favor of the com-
pressed air loudspeaker. This latter con-
sisted of an air compressor, air storage
tank, and electrically-controlled valve.
This valve was connected in series with
a potential and a light sensitive cell
(selenium). The valve varied the com-
pressed air, and successfully produced
sound which could be heard for a distance
of four or five city streets. A similar
compressed air loudspeaker was manufac-
tured by the A^ictor Talking Machine Co.
and was sold under the trade name of the
"Auxetophone."

Lauste's Contributions

It cannot be rightly denied that it was
Lauste who made the first successful sound
pictures. It is a matter of regret that the
many improvements made since Lauste's
time were not made just a little earlier
so that the fruits of this brilliant investiga-

tor's work might have been reaped by him.
As it was, Lauste merely smoothed out
the road of those who followed him, as
is so very often the case with pioneers in
any field of endeavor.

Projectionists will find much of interest
tc them in the work of- Eugene A. Lauste,
for it was he who made some of the most
important contributions to the development
of the motion picture projector. The
proof of Lauste's fine mechanical talents
is contained in the accompanying illustra-
tions which show conclusively that this
man certainly was far ahead of any of
his contemporaries.

References

English Pat. No. 18,057, Aug. 11, 1906.
10,526, May 3, 1912.

16.941, Nov. 4, 1912.

16.942, Nov. 4, 1912.

U. S. Pat. Ser. No. 764,946, May 1, 1913.
Daily Express (Loncl.), Aug. 28. 1913.
Daily Chronicle (Lor.d.1, Aug. 27, 1913.
Film Censor Exhib. Rev., Sept. 3, 1913.
Cinema (Lond.), Sept. 3, 1913.
Scient. Amer-, Dec. 22, '1917.
Elect. Exper., Tune, 1918.
Pictures & Picture Goer, May 3, 1919.
Motion Picture News, July 26, 1919.
Science cr Invention, Dec, 1920.

Photo Electric Cell Fatigue

Recent comments ip technical papers anent
the "fatigue" and "lag" characteristics of
photo electric cells prompted the invitation
to the following workers in the art for their
opinions on the subject. We are told,
among other things, that cells must not be
exposed to light when not in use and that
certain cells display a definite "lag" char-
acteristic. Both characteristics are dis-
cussed in the following interesting com-
ments.— The Editor.

A. J. McMASTER,
G-M Laboratories,
Chicago, Illinois: —

THE interesting question as to whether
photo electric cells of the alkali metal
type are subject to depreciation when not in
use, and particularly when such cells are
exposed to light, has been discussed pro and
con for a number of years. Some cells do
show depreciation of this sort, although in
a final analysis it is generally found that
the loss of sensitivity is not due to ex-
posure to light but is inherent in the
particular cell in question.

In normal operation, exposure to light
produces emission of electrons from the
sensitive surface of the cell, which negative
charges are replaced by the source of po-
tential connected in the external circuit of
the cell. When the battery is omitted or
the circuit is open, electronic emission oc-
curs upon exposure to light, but a state of
equilibrium is almost instantaneously
reached which inhibits further discharge
of negative electricity.

Although it is the writer's opinion that
no deleterious effects are produced by ex-
posure of a high quality photo electric cell
to light when the cell is not in use, it is
highly recommended that cells of the alkali
metal type not be exposed to strong direct
sunlight or intense incandescent sources at
close range, due to the marked depreciation
caused by the heating of the cell.

As the materials used in some types of
cells have a very low melting point, the
effect of even moderate heat is to practi-
cally destroy the usefulness of the device.

As mentioned above, some cells show
rapid depreciation with time whether in

light or in darkness. This effect is due to
the chemical action within the cell as a
result of improper preparation of materials.
Undoubtedly the purity of materials used
and the amount of care exercised in evacu-
ating the envelope are of primary impor-
tance in the manufacture of a quality
product of this kind.

The subject "fatigue" has many ramifi-
cations and a long story could be written
about the same without perhaps convincing
anyone of the truth of the matter. How-
ever, I believe that your editorial policy
in this regard will bring to light interest-
ing information of considerable value to
your readers.

DONALD H. LOUGHRIDGE,
R. C. Burt Laboratories,
Pasadena, California: —

I agree thoroughly with the recent
statement of Samuel Wein in your columns
to the effect that a great deal of this talk
in regard to the necessity of keeping photo
electric cells in the dark is mostly funda-
mentalism.

Our experience with various types of
cells has shown that in the modern type of
cell fatigue is practically absent, and ex-
posure even to bright sunlight for as long
as eight hours with maximum current
being taken from the cell at all times shows
absolutely no change in the sensitivity of
the cell.

SAMUEL WEIN,
Radiovision Corp.,
New York City: —

Among the comments on photo electric
cells which you submitted to me are the
following: (1) photo electric cells, if ex-
posed to a strong source of illumination,
are subject to fatigue and require some
Hi tie time period before they are fit for
further use, and (2) it requires several
minutes after certain cells are connected
to a source of potential for them to func-
tion properlyi. That both comments have
no basis in fact will be shown presently.

Before we go into the subject matter
proper, it would be best if we have a defini-
tion of terms.

Fatigue: Webster's Dictionary tells us
that it is a "state of exhaustion" or "tired."

Lag: The same source tells us that
this is to "move slowly" and also to "stay
behind."

Let us now see what bearing these defini-
tions have on the photo electric effect.
Fatigue as applied to photo electrons would
be a gradual decrease in the photo electric
emission with the same source of light.
Whereas, lag would be an inertia of the
cell in responding to a light change. Let
us see if it is possible to give a practical
analogy to these effects.

When a battery is in continual use, its
output continuously decreases : this would
correspond to fatigue. On the other hand,
if a potential is applied to a motor, the
latter will require a few seconds for .its
armature to reach uniform and maximum
speed: this corresponds to lag. As a mat-
ter of fact, if the potential applied to a
motor is switched on and off several times
in quick succession, the motor itself will
not respond to these "on and off" periods
of potential.

Thus we see that there is a marked dif-
ference between "fatigue" and "lag,"
although both these terms are loosely ap-
plied by some writers.

As a matter of fact, the true photo elec-
tric effect will exhibit no lag or fatigue
characteristics. However, if a cell does
show these characteristics, it will be be-
cause of (1) the absorption of occluded
gases of the alkali metal or its correspond-
ing hydride, forming, as it does, a chemical
reaction, i.e., an "oxide," (2) a gradual or
slow seeping of air into the cell (3) a
gradual change of the alkali metal surface,
and (4) the most probable cause, a faulty
amplifier to which the output of the cell is
connected.

Much of the difficulty experienced with
photo electric cells may be traced directly
to the "grid resistor" connected in series
with the cell and directly across the "grid"
of the first amplifier tube. This resistor is
very unstable and not only varies its char-
acteristics with the temperature of the room
but also with the humidity and the amount
of current flowing through it. On the other
hand, if a transformer-coupling is used with
the cell, this grid resistor difficulty is over-
come. One company uses a high resistance
unit in series with the photo electric cell
and transformer as a means for protecting
the cell from over-loading.

Another difficulty experienced with photo-
electric cell amplification is "current leak-
age" across the base of the cell. This is
sometimes attributed to the cell proper, but
it is known that this leakage may be elimi-
nated by taking the leads out of the cell at
opposite ends, such as is now done by cer-
tain manufacturers.

The conclusions to be drawn from the
foregoing are that the photo electric cell
possesses no inertia or lag and hardly
enough fatigue to be noticeable. Such dif-
ficulties as have developed are the fault
of the apparatus used with the cell.

THE SEILER EXPERIMENT:—

Miss Seiler1, a student of Professor Kunz
at the University of Illinois, undertook to
ascertain whether a long period of "illumi-
nation" of a "hard vacuum" or "hydride"
cell would give rise to fatigue. To do this-

* Astrophys. Jour. Vol. 52, p. 129, 1920.

November, 1929

The Motion Picture Projectionist

she tested certain cells for a period of more
than 1,000 honrs, during which time she
observed at regular intervals the gal-
vanometer deflections, the while keeping
the temperature, intensity of light, and the
source of potential (110 volts), constant
at all times.

After 520 hours' exposure to a strong-
source of light the cell had increased in
sensitiveness by a considerable degree. The
galvanometer deflections began with 176
mm. and gradually increased to 300 mm. at
the end of the exposure period. The potas-
sium hydride cell, on the other hand, under
the same conditions excepting that the ap-
plied voltage was 36, showed no exceptional
constancy. Slight fluctuations occurred dur-
ing the exposures, the initial and final gal-
vanometer readings were 194 mm. and 191
mm., respectively, showing that fatigue was
l egligible.

These same two cells were exposed for
60 hours without continuously applying a
voltage. ■ At the time the photo electric
galvanometer deflections were taken, 110
volts was applied to the potassium cell and
27 volts to the potassium hydride cell. All
conditions remained constant throughout
the experiment.

The results showed an increase in sensi-
tiveness for both cells, the initial and final
deflections for the potassium hydride cell
being 196 mm. and 316 mm. It seems
strange that the mere exposure to light,
without the passage of a photo electric cur-
rent, should increase the sensitiveness so
much more rapidly than when the applied
voltage caused a current flow through the
cells. Both investigations, however, point to
a negative conclusion with regard to a
fatigue effect.

New Film Patches

THAT motion picture projection is un-
dergoing a refining process constant-
ly even in the smallest details is evident
by the many suggestions for improve-
ment in such an item, for example, as film
patches. Film patches in themselves are
very important, as every projectionist
knows, yet the fact that in this stage of
motion picture development — what with
sound film, color, and third dimension be-
ing the salient features of creative work
—it is interesting to note that other phases
of motion picture technique are not being
neglected.

An improperly made film patch is the
cause of many breaks in a show, interrup-
tions which are costly to all branches of
the industry. It really seems as if there
is nothing as irritating as to have an in-
teresting motion picture suddenly termi-
nated. The film patch is often the reason
for this.

What follows will demonstrate that the
film patch is anything but insignificant in
-the scheme of things projection. Many
projectionists, with years of experience,
have come to regard film patches as a
mere detail of their daily routine. And
so they are, but carelessness in this detail
is inexcusable — particularly so for the ex-
perienced projectionist.

Causes of Film Tearing

A few words anent the causes of film
tearing will not be amiss at this time.
Summed up, these causes are as follows :

0 0 0 0 0 0

0 0 0 0 0

010 0 0 0

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Figure 1

(J) Brittle film, due to a dried condition
(2) Continuous wear on the film by me-
chanical parts (3) Abuse of film in han-
dling, such as too rapid rewinding and (4)
Opening of a poorly made patch.

We shall not concern ourselves at pres-
ent with the causes of film tearing other
than to offer the above summary, but we

shall discuss the manner of making correct
splices and shall offer details on methods
recently outlined for improving this im-
portant detail.

In Figure 1 is seen the common type of
patch, well-known to all projectionists. It
is made by cutting both ends of the him
and disposing of the emulsion by moisten-
ing and removing it with a razor blade or
some other sharp instrument. The film
cement is thereafter applied to both ends,
which are then brought together and sub-
jected to pressure for a few seconds.
Proper sprocket hole alignment is essential
in this operation.

New-Type Patches

Lyman1 in Figures 2 and 3 shows a
new method for splicing. The film is cut

Figure 2

to form a tapered end bluntly rounded to
form an apex. The extent of the overlap
is less than the complete tapered portion.
There is thus left at each end of the film

4— 144

6j 3 7 n

Mnnn rrfo rAn'fi ^An n nbn

U U UJU L) L! U 0/Ul! pUU U'UU U

/v ft
Figure 4

a notch opposite the patch. The length of
the notch is less than that of a picture
area or of the distance between successive
perforations. Other forms of patches
make use of a piece of celluloid holding
together two ends of film, with a space be-
tween th'e perforations.

McLaughlin and Swing2 show their
method of forming a patch in Figure 4.
The two ends of the film are cut so as to
give it a concave edge, as at 9 in the draw-
ing, on the edge of the film. This pre-
sents a curved seam, 10, of no greater width
than is usual but obviously having an in-
creased superficial area. The radius of the
cut edges, 8 and 9, will ordinarily be the
same, but this radius may be varied as pre-
ferred from that shown, in which the length
of the radius is substantially equal to the
length of the chord. This presents a central
extending tab portion as the film is ad-
vanced in one direction and opposed ele-
ments at the ends of the edge, 9, when
moved in an opposite direction.

Experiments have demonstrated that a
lapped joint made in this manner is ap-
preciably stronger and less liable to sepa-
rate than a patch in which the edges are
cut squarely across.

REFERENCES

1 U. S. Patent No. 1,727,349, Sept. 10, 1929.
- V. S. Patent No. 1,728,974, Sept. 24, 1929.

r-H

Figure 3

Paper Sound Track Patch

A reader, Mr. A. Caminetsky, of Brook-
lyn, N. Y. recommends the pasting of a
gummed piece of paper of a size exactly
the same as the recommended sound film
patch over the patched portion of the
sound track. It is claimed by him that
with the black Movietone lacquer there is
a slight click audible in the horns as the
splice passes through the sound gate. Mr.
Caminetsky is right in this contention, but
we hardly can see where his suggested
method offers any improvement.

Danger of Lint

Gummed paper such as is suggested by
Mr. Caminetsky is likely to peel when
subjected to heat, or lint from the paper
is very likely to clog the film gate. Al-
though it is denied that the paper, once
tightly applied to the film, will either p'eel
or give off lint, the practice is too fraught
with possible serious consequences to merit
a recommendation.

Mr. Caminetsky's suggestion is centered
about the fact that the noise occasioned by
the paper-covered splice as it passes
through the sound gate is below IS cycles
and -thus below the threshold of audibility.

The Motion Picture Projectionist

THE BURT REPRODUCER

FOR TALKING MOTION PICTURES

Burt Reproducer on Powers Projector
Features

Synchronous Motor Drive (110 or 220 volts, 50 or 60 cycles). Pre-
vents variation in speed from variation in line voltage, or projection
load.

The Super Cells used require only two stages in head amplifier, hence
less distortion.

Ease of Threading. When running disk or silent, the Sound-on-Film
unit is not threaded. Sound-on-Film threads as easily as through a
Powers gate.

Turn Table Is Accessible, being up high at the side of the machine.

Easy to Install. Installation can be made by the ordinary operator,
and wire man.

Projector Head is driven by its main drive gear and is not required to
drive any part of the sound equipment.

Only Three Shafts: (1) Motor Drive Shaft, (2) Sound Film Shaft,
(3) Disk Table Shaft.

Variable Speed can be used for making schedule by driving the head off
the Powers Motor, when running silent. Change from synchronous
drive to variable speed drive requires about ten seconds.

No Universals — No flexible couplings, flexible shafts, or long unsup-
ported shafts are used, as these produce tremolo.

Fire Hazard Is Decreased by use of this equipment. Failure of take-up
does not cause film to pile up in light.

Write for Bulletin No. 291
Formerly Manufactured by

R. C. BURT SCIENTIFIC LABORATORIES, Pasadena, Calif.

Now Manufactured by

RELTONE CORPORATION, LTD.

9035 VENICE BOULEVARD, LOS ANGELES, CALIF.

PREVENT STOPS

GRIFFIN FILM CEMENT M^.»o»-b„ddi„jr

^ — — — ^ — — patch that stays stuck
Specially Suited for Sound Prints

Manufactured by F. B. GRIFFIN, OSHKOSH, WIS.

FREE SAMPLE and PRICES on request

November, 1929

Television — Present and
Future

{Continued from page 19)

can be done where a number of channels
are available, as in telephone practice. The
total frequency can be separated into a
number of frequency ranges and those of
the higher frequencies transmitted as lower
harmonics to get them into the frequency
range of the present wire channels. Thus,
there may be used 8 or 10 pair of wires to
handle the different frequency ranges that
are again assembled at the receiver. It
might be said that the progress of televi-
sion depends upon improvements in means
for handling the signals between the trans-
mitter and the receiver.

No mention has yet been made of am-
plification, but this phase of television work
follows general radio and sound picture
practices. At the receiving end there will
be banks of amplifiers not only for the
picture signals but for the sound as well.
The sound will be fed into apparatus sim-
ilar to that in use today and thence into
the horns.

Reproducing Process

Reproducing the picture presents, how-
ever, quite a problem, both mechanically
and electrically, for to be of any practical
commercial value, the picture must be as
large as that at present shown on the regu-
lar motion picture screen. Although the
apparatus may finally take the form of a
projector, it is not unlikely that the early
machines will be designed after the fashion
of the tube screen employed by Bell Tele-
phone Laboratories in their television tests
of 1927.

The Bell Laboratories apparatus con-
sisted of a long Neon tube which folded
back on itself to form a square screen as
suggested in Figure 3. For our purpose
this screen would have to be as large as
the present motion picture screen and con-
sist of about 960 separate tubes almost
touching each other. An electrode consist-
ing of a wire spiral runs through each tube
which is filled with neon or another gas
which will cause a glow when a high volt-
age current is applied to it. On the back
of each tube are glued pieces of tinfoil, it
requiring about 960 pieces along each tube
with each piece insulated from the next.
The wiring of this frame would be rather
complicated to show in detail, so its opera-
tion will be explained with the help of Fig-
ure 3.

For the sake of clarity, let us assume
that the incoming television signals have
been amplified and the output of the ampli-
fier connected to the arm A of the row of
segments shown connected to the tinfoil
strips. The voltages have been adjusted
so that the tube at any point will glow at a
brilliancy equal to the light value of the
spot which is before the photo electric cell
at the transmitter. Then if the arm A is
on the contact connected to the upper left-
hand tinfoil, a light will be produced at
that point equal to the light falling on the
photo electric cell when the scanning disc
has just started across the picture.

Now consider the contact arm at the
receiver moving in perfect synchronism

November, 1929

The Motion Picture Projectionist

Electrical Energy

The power that is transmitted by any
electric circuit depends on the current and
the voltage. The unit, the watt, is the
amount of power obtained from one ampere
at one volt. This unit is too small for
ordinary purposes and the kilowatt equal
to 1000 watts is used.

For D. C. circuits :

W = IxE
W = Power in watts
I = Current in amperes
E = Electromotive force in volts

In A. C. circuits the entire current is
not always available for doing work. This
calls for another term in the energy equa-
tion, the power factor, which is the ratio
of the current available for power to the
total current. For single-phase A. C. cir-
cuits the equation becomes

W = IxExP
P = Power factor of the circuit
For two-phase A. C.

W = 2 x I x E x P
For three-phase A. C.

W= 1.73x1 x Ex P

Electrical and Mechanical Conversion
Factors

1 H.P. = 746 watts = .746 kw.

1 kw. —1.344 H.P. =approx. \y3 H.P.

with the disk at the transmitter. As the
light falling on the photo electric cell varies
as the disc moves across the first strip, we
will have light variations along the tube
that are of the same intensity. As the
second hole at the transmitter starts across
the picture, the contact arm at the receiver
is contacting with the second tube and
again the light values are reproduced just
as picked up at the transmitter.

Wire Television First

This action continues until the whole
scene is built up and a complete picture is
shown. The whole picture is shown 20
times a second, thus the eye, as in present-
day motion pictures, gets the effect of a
continual picture. This rather brief
sketch is but a presentation of the basic
principles of television, and we shall not
tarry to figure out how many contacts the
commutator must have. The answer
would be 921,000.

A television system demands perfect syn-
chronism, for the contact arm and disc
must keep in step or the picture will shift.
With wire transmission it is entirely pos-
sible to accomplish this, and the technicali-
ties of the methods available will be pre-
sented in an early issue of this publication.

Thus are the chances of television, con-
sidered in the light of present practice. It
has been said that seventh-grade arithme-
tic is enough to prove television impossi-
ble ; but, after all, mathematics may be
made to prove almost anything one wants
it to prove. It may take years for the
development of a radio televison, but wire
television will be an accomplished fact be-
fore the echoes of "It can't be done" die
out.

IN WESTERN CANADA!

CANADIAN THEATRE SUPPLY CO.

Authorized distributors for

SIMPLEX— MOTIOGRAPH— POWERS— HOLMES

and all theatre equipment of the leading manufacturers. Also, an extensive line of

stage equipment.

Complete Sound Picture Service!

105 Capitol Theatre Building

Winnipeg, Man., Canada

Alberta Representative

M. L. ADAMSON
1605 — 104th St., Edmonton, Alb., Canada

1 d\A SPECIAL
WSmi FEATURES

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QUALITY PROJECTION

t 0Uff T OPERATloK
t CONSTANT VOLX\Ql

Imperial Two Bearing M-G Set

Imperial M-G Sets were designed
after an exhaustive investigation to de-
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Projectionists desired most. These fea-
tures are embodied in the Imperial M-
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highest type of Projection.

Imperial makes
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Systems, Pumps,

a complete line of
>tors for Ventilating
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OUR BUSINESS

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Service

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The Imperial M-G Set raises Projec-
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tract more patronage to your theatre.

Imperial M-G Sets are a high quality
product, attractively priced and
suitable for large and small theatres.
Furnished with ball or sleeve bearings.
Motors up to 30 HP. are self start type,
requiring no expensive compensators
saving both first cost and upkeep. Im-
perial also has a line of Battery Charg-
ing and Emergency Lighting Equip-
ment.

Distributors write for open territory

The Imperial Electric Co.

AKRON, OHIO

OFFICES IN PRINCIPAL CITIES

Mail

for Prices and Circular

| Yon may
■ Prices.

send me Imperial M-G. Circular and

■ Citv

1 Theatre

The Motion Picture Projectionist

November, 1929

Standard Equipment
roc Publix* rex* RKC

ANR OTHER GREAT CIRCUITS

SRECIEIEL Dy RCA RHCTCRHCNE,
INC., CN ALL RCA INSTALLATIONS

WAILIKIEIC

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IT Delivers

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Sharper Definition

Perfect Sound

No Fadeaway

BRILLIANT PROJECTION
WITH LOW INTENSITY

The logical screen for your theatre

Write for Booklet and Sample

WALKER SCREEN CC.

85— 35th Street Brooklyn , N. Y.

Give This to Your Friend — Have Him Fill It in and Mail to us at Once

The Motion Picture Projectionist
45 West 45th Street, New York City
Gentlemen :

Enclosed please find $2.00 for which enter my subscription for one

year (12 issues) starting with issue. (Two years, $3.00.)

Name ;

Street ■.

City

Color Process

(Continued from page 25)

reconstructed by presenting each transpar-
ency with its proper filter in a viewing in-
strument. This may be done by projection
with the use of a triple lantern, in which
case the red, green and blue transparencies
will be projected simultaneously from the
lantern forming one picture in natural
color on the screen. This process of color
photography reached its highest develop-
ment in the hands of Mr. F. E. Ives, whose
Kromscope has never been surpassed for
absolute fidelity in color photography.

The triple lantern is wasteful of light,
and there are other defects in the additive
process which make it somewhat unsatis-
factory commercially. The subtractive
process is a more commercial method and
is much more widely used. In subtractive
processes the three negatives through the
red, green, and blue filters are taken as in
the additive process but they are printed
to be used as superimposed prints, each
print being made in a color which is com-
plementary to the taking filter.

The Subtractive Process

Let us consider our discussion of the sub-
tractive process as confined to still photog-
raphy in the making of prints. When we
print from the red sensation negative we
are printing from the thinner parts of those
parts which represent the absence of red
in the subject, hence the red sensation nega-
tive must be printed not in red but in a
color which completely absorbs all red. In
other words, the red negative is printed in
its complementary color — that is, blue-
green. The green negative, therefore, will
be printed as magenta, and the blue nega-
tive as yellow.

Superimposed in full strength these
colors absorb all color, and the result is
either black or gray, according to the
amount of light reflected. Intermediate
colors are produced by the mixture in va-
rious proportions of the three fundamental
colors ; while the total absence of color
will produce white, provided we are print-
ing, for example, on white paper or if we
are printing a transparency to be viewed
by white light. It will be observed that
in this case we start with white light from
which we produce color by subtracting va-
rious colors, hence the name "subtractive
process."

How Processes Differ

These two processes may be differen-
tiated one from the other very simply as-
follows : The additive process is one in
which we start with colored light from:
which we produce white ; while the sub-
tractive process in one in which we start
with white light and from which we pro-
duce colors by subtracting various colors.

The present-day commercial processes
are most generally based upon the subtrac-
tive principle and it is quite probable that
those processes which will be most suc-
cessful commercially, from the motion pic-
ture viewpoint, will be those making use
of this principle.

November, 1929

The Motion Picture Projectionist

Care and Maintenance of
Motors and Generators

SYSTEMATIC inspection at least
once a week is necessary to insure
the best operation of motors and genera-
tors and the following points should be
given special attention and consideration.

Both the interior and exterior of ma-
chines should be kept free from water,
oil, dirt and grease. For machines in-
stalled in very dirty places, troubles may
be averted by periodically removing the
rotor or armature and thoroughly cleaning
the machine.

Cleanliness

A vacuum cleaner is highly recom-
mended for cleaning assembled machines.
The use of compressed air is not recom-
mended on assembled alternating current
motors. It is especially objectionable on
machines installed in locations where there
is much carbon dust, metallic chips, etc.,
as the compressed air may drive the dirt
or metallic chips into the windings and
cause break-downs. On direct current ma-
chines the use of compressed air is not
objectionable because all the parts are
more or less accessible, especially the com-
mutator and brushes.

Lubrication

Bearings — The life of bearings is af-
fected by the lubrication, belt tension and
alignment of the driving and driven shafts.
Excessive wear and heating of all bear-
ings can be reduced to a minimum by ade-
quate lubrication, proper belt tension and
accurate alignment. When bearings are
unduly worn, they should be replaced, and
after the new bearings have been put in,
the air gap should be tested to see that
it is uniform all around.

Oil wells should be filled with petroleum
oil (not vegetable or animal oil) through
the oil filters, while the machine is at stand-
still, up to within 1/16 in. of the top of
the oil filler. Experience has shown that
animal or vegetable oils or greases, or
admixtures of them with mineral or
petroleum oil will dry and gum, and by
gumming ducts and oil rings, prevent the
free flow of oil to the bearings.

Incorrect oil level may be experienced
if the oil wells are filled while the motor
is running. After a motor has operated
for the first week, the oil should be drawn
off and the bearings washed out with kero-
sene, to wash out all- sediment before re-
filling the bearings with oil. The drainage
plugs should be taken out and dipped in a
mixture of red lead and shellac and then
replaced and tightened securely to prevent
leakage.

The bearings should be refilled at regu-
lar intervals, the frequency depending
upon local conditions, such as cleanliness,
severity or continuity of service, etc.
After changing the oil, the oil rings should
always be inspected to make sure that they
are in their proper position and turn freely.

Brushes

Tension — The brushes should be in-
spected to see that they move freely in
the holders and at the same time make
firm, even contact with the commutator.
(Continued on page 48)

UPCO ELECTRIC PICK-UP

IT* SPECIALLY adapted for motion picture theatre sound reproduction.
*-J Brings out the richness and brilliant qualities of modern recording.
Ball-bearing yoke action and ball-bearing base pivot combine with scientifi-
cally correct weight and free needle action to bring about an absolute
minimum of record surface wear. Available in any desired over-all length.
Also built to special specifications. Now being used in hundreds of motion
picture theatres.

Recommended by

'y«\ Projectionists

Write for samples and full details

UPCO PRODUCTS CORP.

A. BORSUK, President

Maker of Acoustic Instruments for Over 13 Years
270 LAFAYETTE STREET NEW YORK, N. Y.

Not connected with any other firm in the industry

RAVEN TRAnl

MONTHS of experimenting and developing under
the supervision of New York's most expert pro-
jectionists and theatre executives have created a

PERFECT SCREEN

AS PROOF

ALL LOEW THEATRES EVERYWHERE

and many others are being equipped with this new

RAVEN SOUND SCREEN

•HIS IS A TRIBUTE TO SUIT THE MOST EXACTING THEATRE.
TRANSTONE WILL SOLVE YOUR SOUND PROBLEMS, TOO.

RAVEN SCREEN CORP.

1476 Broad-way

NEW YORK

The Motion Picture Projectionist

ovember,

1929

tione

Are ^lOl

in line to supply the fans *)

with What They Want •

INSTALL

SyNCCCDISft

SYNCHRONIZED TLCN TABLES

Perhaps you have been under the impression that it takes thousands of
dollars to equip your theatre for talking pictures? If so, we suggest that
you get in touch with us and learn all the details of Syncrodisk Synchro-
nized Turn Tables —

complete for only

500

Patrons are demanding talkies and they are going
to the houses which show them. Get in line now
at this low price.

HIGH POINTS

Spring Suspension: The Syncrodisk patent
that spells steady even motion.

Metal Guard surrounding the disk has two
pockets for needles.

Not Driven Off Intermittent

Installation: Can be made by any operator
and wire man. In one hour you are ready
to run the standard 16" synchronized
disks.

Comes Complete with two pick-ups and
change-over fader.

More than 300 now performing smoothly
every day.

Supplied with two Wright-DeCoster Speak-
ers and one Amplifier for $750.00.

HENRY A. LUBE

European Distributor, 118 Blv'd Haussmann, Paris, France

Radio Motion Picture Co., 156 W. 44th St., New York

Weber Machine Corporation

59 RUTTER ST., ROCHESTER, N. Y.

Auditorium Acoustics

By S. BAGNO
II

THE simplest yet most reliable test
for reverberation is to clap the hands
smartly together, and then to note the time
for the sound to die down completely.
This is a rough approximation of the re-
verberant period of any orifice ; it will
also enable the hearer to find the most pro-
nounced source of echo. The use of a
piano enables one to test for many fre-
quencies, and will give a fair idea of the
acoustical characteristics of a theatre for
the entire musical scale.

The effect of reverberation is different
for speech and music. Whereas speech be-
comes less intelligible with increasing re-
verberation, music is given an impression
of depth that is entirely lacking out in
the open air. The average reverberation
period for a music hall should be about
25 per cent, greater than for one designed
entirely for speech.

Besonance

Another problem is that of resonance.
Resonance is a forced vibration of any sec-
tion of the orifice, due to the fact that it is
1 uned exactly to the same frequency as the
source of sound. Not only the air in a
theatre may cause it to act as a large
organ pipe, but the walls, woodwork and
ceiling may act as a large selective sound-
ing board. When this occurs, certain notes
may be so much amplified above the rest
of the sound as to be jarring to one's
nerves, and certain overtones in speech
may become so loud as to make the rest
of the harmonics seem badly distorted.

This destroys the original quality of the
speech. Often, when the second harmonic
of the voice is unduly amplified, a rich
baritone . sounds like a piping soprano.
More often,, the fundamental is magnified
and the voice sounds like a low-pitched
growl.

Resonance may foe detected in several
ways. Perhaps the easiest way is by
whistling; although the usual practice is
to have someone sing up and down the
musical scale to detect whether the thea-

Equipment Troubles and
Maintenance

(Continued from page 28)
fader binding posts. This point is the
electrical center of the first half of the
system. If sound is heard at this point,
then we may safely assume that the trouble
is in the control section of the system.

When listening at the output of the
amplifiers with a headset, it is well to re-
member that a headset should not be worn
on the head, as the volume at this point is
sufficient to occasion serious damage to
the ear drums. Care should also be taken
not to get one's fingers across the binding
posts at this point, as the voltage is quite
high and may give one a serious shock.

A majority of "no sound" troubles may
foe traced to some small detail of the sys-
tem, suoh as a pulled plug, dirty contact
or loose connection. In succeeding issues
we shall discuss each section of the equip-
ment in detail with regard to trouble
shooting.

November, 1929

The Motion Picture Projectionist

A Warning

and Some

Good Advice

Editorial from

EXHIBITORS HERALD WORLD

Of May 4, 1929.

TECHNICAL ADVICE.
When an exhibitor sets out to obtain
advice and guidance on the seh\etl°" t?e
sound reproducing equipment for his theatre
he should bear well in mind that the prob
lem at hand is not a theatrical one not
an ordinary matter of showmanship and not
a question of a type which a lifetime about
a theatre would necessarily qualify a person

t%Phe0ns°eTectionPOo"- sound reproducing equip-
ment for a theatre involves some very ex«t
technical questions and the advice and guid-
ance of a competent technician is not only
desirable but absolutely essential.

A MACY HORN WILL IMPROVE
ANY INSTALLATION 100%

Model S-120 Is a Perfect Sound Re-
producer

Extremely easy to install. No loss of
pitch, no drumming tone, withstands all
climatic conditions because made of the
finest acoustic properties,

Especially Recommended for
THEATRES — ICE SKATING RINKS —
DANCE HALLS — LARGE AUDITOR-
IUMS. CHURCHES, etc.

THE MOST IMPORTANT THING
IN "TALKIES"

Is the sound1 effect on the ears of
your critical audience.

GOOD SOUND

Is More Important Than Good
Pictures

Today perfect tone reproduction is of
paramount importance and failure to main-
tain your sound reproduction to the high-
est standard means actual loss of patron-
age for now the public go where they hear
the best "talkies."

If you have not a MACY HORN you
have not the best "talkies."

Macy Acoustic Engineers Are at Your Service

Booklet on Request

MACY MANUFACTURING CORP.

Largest Horn Makers Supplying
the Theatrical World.

451—39 th St., Brooklyn, N. Y.

tre reenforces any note or notes. This
reenforcement will repeat itself for several
octaves, as the body, or air column, vi-
brates in sections. The lowest pitch to
which it responds is the natural frequency
of the resonant body.

The presence of resonance in a small
quantity is desirable, because it tends to
strengthen the original sound. Resonance
is usually eliminated by damping the vib-
rating body. This is accomplished by put-
ting a soft, pliable substance, such as cloth,
against it. When an air column is vibrat-
ing in resonance, it may be damped by
covering its walls with sound absorbing

materials. T c

Interference

Like resonance, interference will affect
only certain components — the components
that are also affected by the resonance of
the air column in the theatre itself. This
condition is most evident in rectangular-
shaped theatres. The property of inter-
ference consists in the sound reenforcing
itself in one portion of a theatre with the
reflected vibrations from the walls, and
opposing each other in other parts of a
theatre. This point may be illustrated by
the waving of one end of a rope the other
end of which is tied down. If the motion
of the hand corresponds to the natural fre-
quency of the rope, the entire rope will
bob up and down. If, now,, the frequency
of the rope be doubled, the rope will vi-
brate in two sections, while the middle of
the rope will appear to be still. Here we
have reenforcement and interference. The
vibrating sections of the rope may be con-
sidered the reenforcement sections, and the
middle may be considered the reenforce-
ment section.

This is almost a perfect analogy to the
condition encountered in any air column as
the waves are reflected from the walls and
add to and interfere with the waves com-
ing to the wall. Interference at high fre-
quencies is negligible because the human
ears, because of their distance apart, tend
to balance out their effect. Although in-
terference may be quite marked at lower
frequencies, it may also be discounted be-
cause it does not interfere with our per-
ception of the intelligence of sound.

When interference becomes too marked,
as sometimes happens when the reflections
from the roof interfere with the sound
coming to the theatre balconies, it usually
may be eliminated by padding the reflect-
ing medium, or by keeping the sound off
the ceiling by specially shaped baffles of
horns, such as are used by RCA Photo-
phone and Western Electric.
Focusing

Another acoustical defect which gives
the impression of sound coming from a
direction other than the screen, and which
often causes many in the audience to keep
turning their heads to locate the source of
the sound,, is focusing. Sound, like light,
can be reflected and focused from its
source to any other point in a theatre. A
circular dome has the same effect on sound
as has a concave mirror on light : — it con-
centrates it tc one point. To the audience
such a condition will give rise to the im-
pression that the sound is coming directly
from the dome.

The only method which has been found
to work to advantage in correcting this

All About

PROJECTION

Including Sound

By F. H. Richardson
In Three Handsome Volumes

Over 1400 pages of subject mat-
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No projectionist, no theatre man-
ager can afford to be without this
finest of projection libraries.

Volumes I and II covers the sub-
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III, just published, is devoted en-
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Each volume contains Richardson's com-
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Volumes I and II $6.20 postpaid
Volume III alone $5.10 postpaid

The complete set $10.25 postpaid
(Immediate Delivery)

BOOK DIVISION

CHALMERS PUBLISHING CO.

516 Fifth Ave., New York, N. Y.

condition is to keep the source of the
sound shielded from such a dome by the
same means as were described in over-
coming interference — directional baffles.
These baffles come very near eliminating
all troubles from this source.

The proper time to consider the acous-
tical character of any auditorium is at the
time of the initial design. Technicians may
not appreciate the fact that a large portion
of the theatre-going public are aware of
whether a theatre has good acoustics or not,
but it is a fact nevertheless.

The Motion Picture Projectionist

November, 1929

That Extra Tire

on Your Car

Why do you carry it? You may go a year
without needing it.

BUT IT'S THERE — ready for emergency.
Your current supply may cause you far
greater loss — equally without warning.

Are You Prepared ?

Have you a. "Spare" Trans verter ready to
throw in — into the emergency?

Good business — to have it always ready.

Sold in the U.S.A. by

The National Theatre Supply Co.

Canadian Distributors
Perkins Electric, Ltd.

THE HERTNER ELECTRIC COMPANY

12688 Elmwood Avenue

Wmr^mrt

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Exclusive Manufacturers of the Transverter

PHOTO-CELLS, neon lamps, special
high vacuum or gas filled tubes, and
noise-free liquid grid leaks, manufactured
to specifications.

ARGCO LABORATORIES, Inc.

150 West 22nd Street New York City

Sound Projection
Hints

By R. H. McCullough
Fox West Coast Theatres

THE Western Electric photo electric
cell amplifier cradle should always
swing freely. The rubber base has a
tendency to swell, pushing the amplifier
upwards and causing it to touch the hous-
ing. If such is the case, the rubber should
be replaced to avoid mechanical noise in
the pick-up. Inspect the cradle swing
supports and see that they are of proper
length.

It is imperative that the Movietone light
gate be cleaned before threading the pro-
jector for sound film presentation. All
projector bases should be permanently
grounded. Do not allow any outside
source of light to come in contact with the
photo electric cell compartment during the
time the film attachment is in operation,
other than that which comes from the
exciter lamp. Avoid placing microphonic
tubes in the first socket of the photo elec-
tric cell amplifier.

A hum will be perceptible if the sprocket
perforations project over in the sound
aperture. Keep sprockets and idlers clean
at all times. Before starting the projec-
tor, observe the meter readings and set at
normal operating values. The projectionist
is entirely responsible for efficient opera-
tion of his equipment, thus a thorough
check should be made of all units prior to
running the show.

Photo Electric Cell

The photo electric cell consists of a
glass bulb having two lead wires or con-
nections. The inner surface has a coating
of silver covered with light sensitive ma-
terial of metal potassium. The negative or
cathode lead is connected to this surface.

1-A PHOTO ELECTRIC CELL

Note the cathode lead, which is at-
tached to the inner surface of the cell.
Also note the anode lead, which is
connected to the ring-shaped conductor
inside of the cell

November, 1929

The Motion Picture Projectionist

An opening is left on one side of the bulb,
which serves as a window for the light to
•enter. A ring-shaped conductor is con-
nected to the anode or positive lead.

When the light sensitive material is not
subjected to light, the argon gas acts as a
non-conductor. When light passes through
the film and reaches the sensitive surface
of the bulb, electrons are set free and are
directed toward the anode by the potential
applied to the cell ; due to this action, the
argon gas becomes ionized and therefore
becomes a conductor. The amount of
light entering the cell controls the current
similar to the valve which controls water

49-A AMPLIFIER

Arrow points to positive P. E. cell
lead. Note how amplifier is supported
by suspended springs for the purpose
of absorbing vibrations caused by pro-
jector working parts. This constant
swinging cause P. E. cell lead to break
loose from connection.

flowing through a pipe. The photo electric
cell is connected to the first stage of am-
plification.

Crackling Noise

From the photo electric cell positive
terminal to the grid leak clip on the
amplifier there is a very small stranded
v.Tire. The constant vibration of the pro-
jector causes the amplifier to swing. This
swinging causes the strands to break in
the soldered connections, but leaving
enough contact to m?.ke connection : thus,
•as the amplifier swings a crackling noise
will be perceptible. Inspect these connec-
tions very closely.

Crackling noise is often caused by the
1 ampere midget fuse in the photo electric
cell "B" battery box being defective.
PEC "B" battery connections must be
soldered. All tube prongs must be prop-
erly inserted in their sockets. Frequently
inspect all connections and make sure that
they have not worked loose.

The Battery Charger

This is a device used for furnishing
direct or pulsating undirectional current to

NEW BEAUTY

for the

SOUND
SCREEN

ASTMAN SONOCHROME embraces the
widest range of tinted positive films that
has ever been available for the screen. And
— what is all-important in this new age —
the sixteen delicate Sonochrome tints are
so adjusted as not to interfere with the
faithful reproduction of sound .... Succes-
sors to the tints of the silent era, these
Eastman films bring new color moods —
new beauty — to the sound screen.

EASTMAN KODAK COMPANY

ROCHESTER, NEW YORK

a storage battery for the purpose of re-
charging. The battery charger is like a
pump and the battery is like a tank. The
battery charger must be capable of main-
taining a charging rate sufficient to keep
the battery fully charged.

There are three principal types of al-
ternating current battery charges in use :—
the bulb type, the electrolytic type, and the
vibrating type. Reference to the bulb
type is made here because of its present
use for recharging storage batteries used
in connection with sound equipment. The
bulb type charger consists of a trans-
former connected to the supply line and a
rectifying bulb of the argon type. The
tungar bulb consists of a coiled filament
of wire and a plate a little distance away

from the wire filament. The filament is
made of tungsten and the plate is made
of graphite. The air is drawn out of
these bulbs and they are filled with very
pure argon gas. In all cases the plate of
the rectifiying bulb is connected to the
negative side of the battery to be charged,
while the positive is connected to tube fila-
ment through the transformer winding.

It is extremely important that storage
batteries be not overcharged. Calculate
the battery charging rate. Add the num-
ber of amperes drawn by all the tubes in
the amplifiers, with filaments or plates
drawing current. Multiply the amperes
by the number of hours of use and then
add one-quarter to this amount (to make
(Continued on next page)

The Motion Picture Projectionist

November, 1929

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Advances Made in Color
Photography

ADVANCES in the art of color
photography and projection are cited
in the following excerpt from the report of
the Progress Committee of the S.M.P.E.
as read at the Spring meeting held last
May in New York City. It is apparent
from this report that the majority of
serious research work in this field is being
done by foreign experimenters who have
made many important contributions to the
art. The report follows :

Color Cinematography

There have been no oulstanding advances
recorded in the field of professional color
motion pictures. Lehmann and Kofes in a
long general article have reviewed the
possibilities of two-color photography and
have concluded that a two-color subtractive
process is in general more satisfactory.
The method of manufac.ure of Lognose
color, screen film has been described by
Emmerman. Patents related to three-color
cinematography are in general concerned
with methods of making multi-color screens,
successive exposure through primary filters,
and exposing through prisms to three
images on the area normally occupied by
one picture.

A short description has been published of
the working principles of Keller-Dorian
color films, on the support side of which
horizontal cylinderical lenses of 1-60 mm.
are embossed. Exposure is made through
a three-color diaphragm, the film being
threaded in the camera with emulsion side
away from the lens. Patent protection has
been granted for a number of improvements
in the processes using embossed films.
Wolff-Heide Process

Bourquin has given a description of the
Wolff-Heide two-color additive process.
Pictures are taken with an ordinary motion
picture camera at 28 frames per second,
using film which has alternate frames sen-
sitive to red and blue, respectively. Alter-
nate frames of the print are dyed and the
film projected at 24 frames per second. A
few patents of interest pertaining to two-
color additive 'methods have been issued.

The changed patterns produced by a suit-
able grouping of colored elements moving
slowly past the end of a kaleidoscopic prism
have been reproduced by Jones and Turtle,
using a two-color subtractive process. The

Sound Projection Hints

(Continued from preceding page)

up for battery efficiency). The result is
divided by the number of amperes given
by the charger. The division shows how
many hours the charger should be operated
for the number of hours the amplifiers are
in use.

Salvaging Battery Charger Bulbs
I have found that many projectionists
are discarding quite a few tungar bulbs,
because they are thought to be burned out,
when such is really not the case. Fre-
quently the base of the tube makes an
imperfect contact in the socket and this
causes arcing, with the result that in a
short time the bulb ceases to function and
goes out. Check each tungar bulb before
discarding. Be positively sure that the
bulb and socket contacts are clean and
free from corrosion, before concluding that
the tungar bulb is dead.

November, 1929

The Motion Picture Projectionist

use of such color film for embellishment of
theatre programs is suggested.

Mudrovic has conducted an investigation
on sensitizers and dyers suitable for use in
the bleach-out process whereby film is
coated with a mixture of three primary
color dyes which bleach out in direct pro-
portion to the amount and color of the
exposure light reaching them during the
exposure.

A chemical process cell Pathechrome has
been announced to replace the old stencil
process of Pathecolor.

Subtractive color processes for which
patents have been issued recently are re-
lated to imbibition printing, apparatus for
exact registering of two films, production
of double-width, double-coated film for
recording two pairs of images in four
colors, etc.

Amateur Color Cinematography

An additive process of three-color cine-
matography using 16 mm. film was an-
nounced in August. 1928. A three-color
filter is used on bo.h the standard camera
and projector and a series of tiny cylindri-
cal lenses are embossed vertically on the
film support. The film is threaded in the
camera with the emulsion side away from
the lens so that the light passes through
the embossed lenses before it reaches the
emulsion. Each minute lens element images
the three color filter diaphragm and thus
exposes one, two or three lines on the film
according as the subject reflects one, two,
or all three primary colors.

On projection, the lens elements and the
filters serve to recombine the colors of the
original subject. The film is developed by a
reversal process.

In another new amateur color process, al-
ternate color records are exposed on a film
moving 26-28 frames per second, through a
rotating sector wheel, each filter of which
is made up of seven sectors of different
colors. A reduction in color fringing and
improved color rendering is claimed.

Fire-Proofed Paper Scenery

A new kind of theatrical scenery, capable
of cutting the cost of that item of a modern
stage production from many thousands of
dollars to not much more than as many
cents, was tried out recently in the Grand
Theatre in Geneva, Switzerland, the home
of the League of Nations. The new
scenery is made of brilliantly colored
paper, impregnated with chemicals to
make it relatively fire-proof and illumi-
nated both from in front and from behind
by skilfully placed electric lights. The
partial transparency of the paper is said to
be an advantage, since the use of special
lights shining through the paper permits
beautiful effects not obtainable at all with
present-day conventional scenery.

Very Low Cost

The scenery and decorations for a short
musical production presented between the
acts at the Geneva Theatre cost, it is re-
ported, the equivalent of less than fifty
dollars. The new paper scenery is also far
lighter and less bulky than the ordinary
kinds. That for the Geneva production
could be packed, it is reported, in two ordi-
nary traveler's trunks.

The only reported disadvantage is that
the paper scenery does not last so long as
that built of wood and canvas, but in the
light of its low cost it is claimed that this
is not especially important.

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The Daily Grind

There is a good deal of solemn non-
sense being written about the elimination
of hard work from industry. The tug
and strain, fret and sweat of the daily
job are supposed to have disappeared
among the unskilled, and, as for the skilled,
why, they are supposed to have reached a
state of performing mere parlor tricks.

But for these sentimentalists, let them
follow the bricklayer who lays his hundreds
of bricks in eight hours, when the ther-
mometer hovers near 95 degrees. Or let
them keep up with the carpenter mounted
on the cone of a slate roof, sawing out a
dormer window. Or let them chase the
plumber, or the lineman, tying in, or the
inside wireman pent up in a narrow space

between four walls, while the summer's
sun sends the mercury up to 95.

No, there is a lot of the old pain left in
the daily grind. There is a lot that calls
for nerve, patience, dogged stamina, and
the heart of the true athlete. The mil-
lennium is not here; if it were, then em-
ployers would not be so willing to get rid
of the man 45 years old, to make room for
youth, with taut muscles, with daring heart
and patient back.

Machinery has eliminated some drudg-
ery. That is well. But let's not be fooled.
There is still enough of backache, eye-
strain, and heartbreak in manual labor to
confound the theorist, and to make the
servant more than worthy of his hire. —
Electrical Workers' Journal.

The Motion Picture Projectionist

November, 1929

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One that will maintain perfect align-
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give a more constant voltage due to the
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ROTH B1R OTHERS & CO.

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For sale by all Supply Dealers

Projection Advisory Council
Press Luncheon

THE Projection Advisory Council,
whose committee reports and other
activities in the interests of projec-
tion and projectionists have been reported
in these columns from time to time, will
sponsor a luncheon at which President
William F. Canavan of the I. A. T. S. E.
will be the guest of honor at the Hotel
Astor, New York City, on November 14th.
Practically the entire official family of the
Council will be present at this affair, in
addition to many representatives of the
motion picture trade and public press who
will be the guests of the Council for the
occasion.

The significance of this gathering for
projectionists and those interested in the
progress of projection lies in the fact that
at this, the first public gathering of the
Council officers and members, the friends
of projection will have their first oppor-
tunity to discuss with and explain to the
representatives of the press the problems
of projection and the efforts of those with-
in the craft to develop projection technique
to a high point.

Committees at Work

The various committees of the Projection
Advisory Council have been meeting at
regular intervals within the past six
months, and it is expected that the respect-
ive chairmen will be ready shortly to sub-
mit reports of their activities and recom-
mendations.

The luncheon on November 14th is in
line with the announced intention of the
Projection Advisory Council at the time
of its formation to press for a better under-
standing in all quarters of the importance
of projection and a stressing of the new
responsibilities of the projectionist craft
with the coming of sound pictures. The
Council is in no wise interested in the
purely local happenings of projection or-
ganizations but rather in the broad general
aspects of the betterment of projection
work by the craft, the improvement of pro-
jection room design, the junking of anti-
quated or worn-out equipment, and im-
proved physical working conditions for the
individual projectionist.

It is certain that the forthcoming affair
at the Hotel Astor on November 14th is
the first attempt on the part of any indi-
vidual or group to secure recognition of
the responsibilities of the projectionist and
the importance of things projection in the
general scheme of the motion picture thea-
tre. For many years those interested in
the progress of the craft have realized that
there was an urgent need that those within
and without the industry should be better
informed with regard to the technical side
of motion picture production and reproduc-
tion.

Open Forum for Press

This need the Projection Advisory Coun-
cil plans to supply. At the luncheon, Presi-
dent Canavan will address the members of
the press, after which there will be held
an open forum in which the press will
be invited to ask questions on various an-

November, 1929

The Motion Picture Projectionist

gles of projection work. Several specialists
in projection work will be present to an-
swer all queries submitted. President
Canavan's address is expected to take the
form of a broad general outline of the I.
A. T. S. E. organization, with particular
stress being laid upon the manner in which
the craft has thus far discharged its im-
portant responsibilities and its unceasing
preparedness for whatever developments the
future may bring.

Charles F. Eichhorn, Vice-President of
M. P. M. O. U. Local 306 is the Chairman
of the Projection Advisory Council lunch-
eon committee, reports a brisk demand for
tickets for the affair. Mr. Eichhorn dis-
closed that requests for tickets from pro-
jectionists in Massachusetts, New York,
Connecticut, Rhode Island, Pennsylvania,

Charles F. Eichhorn

New Jersey and Ohio have been received
thus far, indicating, he said, that the affair
is provoking much enthusiasm in projec-
tion circles.

"Projectionists everywhere should take
an active interest in the work of the Pro-
jection Advisory Council," said Mr. Eich-
horn, "for here is an organization which,
while being thoroughly disinterested in
purely local organization problems, is mak-
ing a strenuous bid to generate a wide
interest in all quarters in the importance
of the work being done by the craft. Pro-
jectionists as a craft have never had the
opportunity to have discussed by their rep-
resentative leaders the many problems
which are demanding attention just now.

Council Roster Representative

"A glance at the roster of Council of-
ficers and committee heads should be
sufficient to prove that the Council is truly
representative of the craft. Men who have
earned recognition from the entire craft
for their work in some special phase of
projection work have been enrolled in the
campaign which the Council will launch
in behalf of the craft. These men are
willing to give unstintingly of their time
and labor for the success of the enterprise,
(Continued on next page)

Why Projection Experts
Choose Cinephor Lenses

REALIZING how utterly the profits of sustained attendance depend
on perfect projection, more and more leading theatre owners are
using Cinephor lenses exclusively.

Here's how one of the best-known men in the industry explains it :
"After extensive tests with both American and foreign-made objective
lenses, we have installed your Cinephor lenses, and have found them
far superior to any others. They give us a clear field, depth of focus,
and I have especially noticed that the color correction is practically
perfect."

Cinephors have proved their superiority again and again in tests before
experts in projection. They offer you a sound, practical way to build
sustained attendance in your own house through better projection. For
information, write J3ausch & Lomb Optical Co., 654 St. Paul Street,
Rochester, N. Y.

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The Motion Picture Projectionist

November, 1929

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New Exciting Lamp Serves
as Battery Eliminator

Experiments are now being made with
a view to finding an exciting lamp for
sound picture projector systems which will
use raw A.C. and thus dispense with the
need for storage battery supply. The
principle involved in this new lamp is
based on the insensitiveness of a heavy
lamp filament to the ripple, or 60-cycle
alternations, of an A.C. source. In other
words, it has been found that if a thin
filament be used in an exciting lamp, it
would correspond to the 60-cycle varia-
tions ; but, on the other hand, a husky
filament has been found to be insensitive to
the 60-cycle variations, i.e., from an opti-
cal viewpoint, and thus the photo electric
cell may be used in the circuit in which
raw A.C. is fed to the exciting lamp.

A discussion in detail of this new lamp
will appear in the next issue of The
Motion Picture Projectionist.

P. A. C. Press Luncheon

and it seems to me that the least their
efforts should merit is the support of the
craft at large.

"The Council has many plans laid for
important work during the coming year,
and the support of the projectionist craft
as a whole would serve to indicate to its
officers that its efforts were meeting with
the approval of all projectionists. Such
support can have but one result, and that
a determination on the part of Council
officers to increased efforts and a widen-
ing of the scope of their work.

Council Membership

"The response to Council membership
appeals has thus far been encouraging, but
it would greatly facilitate the- work if
more projectionists displayed an active in-
terest in this work to help them in their
work. I feel sure that within a short time
the Council will have proven its worth to
the craft and will receive the support
which its efforts merit. Probably the best
way in which to stimulate membership
would be to have each Local Union desig-
nate one member to represent it in the
Council. In this way it would be unneces-
sary for every member of each Local
Union to join, yet they would have the
advantage of having representation in the
Council work.

"I think this plan would also serve to
increase manifold the value of the Coun-
cil's work, what with the variety of opin-
ions and suggestions which would be
received.

"Projectionists who may be interested
in the work of the Council and who wish
to establish contact with it may do so by
addressing the Council in care of The Mo-
tion Picture Projectionist, which will
forward all communications to the proper
officials."

The luncheon at the Hotel Astor on
November 14th will be served promptly at
12.30. Tickets for the affair may be ob-
tained from Mr. Eichhorn.

November, 1929

The Motion Picture Projectionist

Inventive Trend Shown
by Patents

REVIEW of the patents taken out

the past thirty years shows that they out-
number those taken out in any other field.
The accompanying illustrations graphically
depict the trend of interest on the part of
inventors who applied their talents to solv-
ing one or more problems of the motion
picture within given periods of time. These
two charts cover patent activity during the
years 1918-19 and 1928-29, ten years apart.
Activity During 1918-19

From January, 1918, to June, 1919, the
British Patent Office issued a total of 168
motion picture patents. Ten of these were
concerned with color photography and pro-
jection, 4 with synchronizing sound and
scene, 7 with relief and stereoscopy, 7
with continuous motion projectors, 5 with
mechanisms aiming at preventing film fires
during projection, 17 are apparatuses for
taking pictures, 18 with mechanical sys-
tems for film manufacture, 30 with im-
provements for photography and projec-
tion, 37 with minor modifications to parts
of mechanisms, and 23 sundry inventions.
A graph of this patent activity is presented
in Figure 1.

By contrasting the percentage of the
separate branches to the total number of
patents, we have very clear evidence of the
fact that at the period in question the most
pressing need of the cinema was for the
improvement of its technical means.

Although cinematography was then in
its twentieth year, it had attained but a
limited degree of perfection, both in its
expression and in its means of production.
The inventions which give the highest per-
centage are those dealing with apparatus
for taking the pictures, for projecting
them, and for the mechanical preparation
of the films ; these needs were too urgent
to leave much scope for attempts of a
more ambitious kind. Color, sound, relief,
were attractive ideas, but cinematography
pure and simple had to be perfected in its
essential elements before paying attention
to the superfluous.

Trend During 1928-29

Let us now glance at the patents issued
by the Patent Office, during 1928-1929,
during the same lapse of time. Out of 256
patents, 52 are concerned with color, 57
with synchronism, 21 with stereoscopy, 8
with continuous motion, 10 are mechanisms
to avoid fire, 9 filming apparatus, 5 mech-
anisms for preparing films, 30 for perfect-
ing projection, 23 sundry inventions in the
technical and photographic field.

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This review shows that the highest per-
centage of patents are concerned with syn-
chronization and color ; there is a notice-
able increase in the number of stereo-
scopic inventions, hardly any difference in
the number of those dealing with continu-
ous motion and with anti-fire devices. On
the other hand, we find a striking decrease
in the number of inventions for perfecting
material for film manufacture, filming,
projection and similar devices. All this
tends to demonstrate that, while the pos-
sibilities of further perfecting existing sys-
tems are not overlooked, the spirit of in-
vention is mainly directed to the solution
of three problems which were almost en-
tirely neglected three years ago, but which
today represent the goal of all inventors.
— International Cinematographe.

type. It can dissipate 250 watts and is
furnished in three ranges : J4-10 ohms, 25-
500 ohms, and 100-100,000 ohms. It is
finished in nickel, with mica and asbestos

mpERi

MROSffM

jVARIABILEl StESISTP
IPAtJpemdJma|de|i

USA1

I'll

CLAROSTAT RESISTOR

The Super-power Clarostat is a heavy-
duty adjustable resistor of the compression

insulation and is provided with a long
shaft and special mounting bracket. It is
suitable for use as a heavy-duty line con-
trol, variable speed motor control, plate
voltage control for transmitters, field con-
trol for shunt type generator, and so on.

SIfREOSCOPK C0NTINOUS

30n

2°r

3.3

2.2

18%

•O-E

8,2%

3,1%

3.9%

3,5%

19%

«.7%

7.3%,

Figure 1

Figure 2

The Motion Picture Projectionist

November, 1929

The Oliver Speedometer

A
L
L

T
H
E

O
R

I
G

N
A
L

M
E
T
E
R

OLIVER MANUFACTURING CO.

1705 E. 21st STREET, CLEVELAND, OHIO

Where to Buy Good Equipment

VANCOUVER, CANADA

THE UNITED ELECTRIC CO., LTD. Com-
plete Theatre Equipment Specialists. We
guarantee you live, dependable service and at-
tractive prices. Write or wire for quotations
which will surprise you.

847 Davie St., Vancouver, B. C, Canada

WINNIPEG, CANADA

M. RICE & CO., J. H- Rice, Prop. Lead-
ing equipment dealers in all kinds of pro-
jection room equipment facilities. Representa-
tives of leading equipment manufacturers of the
United States and Canada. All our merchan-
dise guaranteed for performance and stability.
Whatever you want, we will supply it.

WICHITA, KANSAS

SOUTHWEST Theatre Equipment Co., 321
North Main St., Wichita, Kansas. Jobbers
and Distributors of Equipment. Get our prices
on what you need. Address your inquiry, atten-
tion C. D. Peck, Manager, member I. A. T. S. E.
No. 414.

MEMPHIS, TENN.

TURN IT INTO CASH. We pay top prices
for Used PROJECTORS and theatre equip-
ment. What have you?

Monarch Theatre Supply Co.,
395 South Second Street, Memphis, Tenn.

New subscribers have you secured for THE MOTION
HOW PICTURE PROJECTIONIST? Introduce your friend
l\/lanVto t*ie craft's only paper. Take advantage of the present
3 low subscription rate — $1.50 per year.

Do It Now!

Pres. Canavan Addresses
S. M. P. E. Meeting

THROUGH a fortunate coincidence
the American Federation of Labor
was holding its Convention at the Royal
York Hotel in Toronto at the same time
the Society of Motion Picture Engineers
was in session there. Attending the
A. F. of L. Convention was President
William F. Canavan of the I. A. T. S. E.
Through the efforts of P. A. McGuire, of
the International Projector Corp., it was
arranged with President Porter of the
Society to have President Canavan address
the Engineers.

There is absolutely no doubt that Presi-
dent Canavan's remarks were extremely
well received by the Society. He is a
finished speaker with the ability to attract
and hold the attention of any body of
men ; and it should be a source of great
satisfaction to projectionists that they are
so well represented on all occasions by
such an outstanding and capable leader.

We regret that we had not time enough
prior to publication of this issue of The
Motion Picture Projectionist to secure
a complete transcript of President Cana-
van's remarks, together with some ex-
cellent photographs of I. A. groups which
were taken during the Toronto meeting.
We anticipate having all this material
ready for publication in the next issue,
and it will give us much satisfaction to
present it therein. Meanwhile, we are able
now to give this brief but highly interest-
ing extract from President Canavan's
address :

"From an experience of many years in
the American trade movement and a
deep intimacy with labor problems, I
know of no group of wage-earners which
has given as much time to the scientific
consideration of their work as the mo-
tion picture projectionists. Frequently in
labor unions it is largely a matter of
better wages and better working condi-
tions, but the motion picture projection-
ists are the outstanding exceptions
among wage-earners who give a very
large part of their time to studying the
scientific aspects of their work."

J. F.

Care of Motors

{Continued from page 37)

The brush tension should be checked
regularly to make sure that the proper
tension (1J4 lbs. to 3 lbs. per sq. in.) is
maintained by the spring.

Fitting — When replacing brushes, they
should be fitted by means of fine sandpaper
folded around the commutator and the
rotor revolved by hand in the desired
direction until a proper fit is obtained.

On some machines, the sandpaper can
be held in place if it is cut to a width
slightly narrower than the commutator,
and the front end of the strip inserted into
one of the narrow slots between commuta-
tor bars (where the mica has been under-
cut), and then folded back around the
commutator by slowly revolving the arma-
ture by hand until the paper moves under
a set of brushes.

Position — An operator should never
shift the position of the brushes unless he
knows positively that the brush position

November, 1929

The Motion Picture Projectionist

Care of Lenses

OPTICAL glass is relatively soft and
for this reason it is very easy to
make the mistake of cleaning a lens too
well. In place of the beautiful black polish
of a new lens there appear little fine
scratches, increasing the surface area po-
tentially capable of being affected by
tarnish. Such lenses give less brilliant
images because of light scatter at the sur-
face.

As precision optics advanced with the
advent of new types of glasses, giving
greater range to the formula variations
due to the greater differences in refrac-
tive index, dispersion and absorption of the
raw material, it was found that some very
suitable glasses were also subject to tarnish
and corrosion. Glasses with a lead consti-
tuent would darken by fumes of sulphur,
found in sewer gases, chemical fumes,
leaking gas jets, etc.

Some glasses, being highly hygroscopic,
would condense moisture upon their sur-
faces,, and this in turn avidly takes up
hydrogen sulphide from sewer gas or illu-
minating gas and in turn attacks the glass
surface with a tarnish. Ammonia fumes
similarly make an alkaline solution. Acid
fumes likewise are picked up by the mois-
ture coating.

Tarnish and Corrosion

The remedy is obvious : keep your lenses
dry and away from dampness. These hy-
groscopic glasses and others that disinte-
grate are avoided, because lens makers
have gained in experience and now have
many other glasses available. In several
cases lens series were recalled and rem-
edied. Greasy lenses may tarnish from
perspiration marks when left for a long
time. Lenses should be blown free of dust
and lint and wiped with clean linen, using
a little moisture from the breath.

It is rather disheartening to the manu-
facturers of lenses to have their cautions
against use of alcohols and acids flouted
from time to time by experts who deliber-
ately advise this remedy for cleaning lens
surfaces. The unfortunate reader of such
articles finds that there is a legitimate
charge for repairs, often for regrinding
and repolishing the damaged surfaces. This
is the only way to renovate a tarnished
lens. Such lenses often work all right,
perhaps with a slight absorption showing
up, and tarnish should not be confused with
yellowing of cement or cracked cement, a
temporary condition, which can be easily
remedied.

is incorrect or it is desired to change the
direction of rotation or the mounting of
the machine. On machines with commu-
tating poles, the position of the brushes is
fixed on the neutral point at the factory
and the position of the brushes on such
machines should never be shifted except
to make changes as indicated in the pre-
vious sentence or for compounding or
parallel operation of generators.

Pigtails— Care should be taken to see
that the pigtails or flexible copper con-
ductors are firmly fastened in place so
that they will carry their full current
from the brush to the brush holder.

HERE'S TONE QUALITY INSURANCE!

You don't have to be at the mercy of fluctuating line voltage. No longer is it neces-
sary to have the tone quality and volume of your talking picture installation go clean
to pieces, because of low input voltage. With the

SUPER-POWER

CIARQSTAT

you can instantly adjust the input voltage and thereby main-
tain the output at any desired point, irrespective of line-
voltage variations. This device is a giant variable resistor.
In several turns of knob it provides a wide resistance range.
Handles 260 watts. Available in 0-10, 25-500, and 200-500,000
ohm ranges, Provided with extra long nipple for mounting
on slate or marble panel, and with special bracket for mount-
ing on bakelite panel. Also ideal for variable speed motor
control, such as on your ventilating fans and blowers, and for
generator field control.

WRITE regarding this device and other CLAROSTAT products
which, having set a high mark in radio, are now available
for the peculiar requirements of the modern motion picture
theatre.

CLAROSTAT MFG. CO., Inc.

295-7 N. 6th St.

Brooklyn, N. Y.

SOUND PROJECTION

DEMANDS THE BEST PROJECTION EQUIPMENT

THE SUPERIOR PROJECTOR

Is Proving to Be the Ideal for All Sound Reproducers.

Many installations of the fol-
lowing reproducers for sound
on film or disc are success-
fully proving its adaptation to
sound projection:

De Forest Phonofilm

Pacent,

RCA Photophone

Western Electric

Etc., etc.

New Rear Shutter, Improved Framing Device, Mask on aperture, combined
with its rugged construction eliminating vibration, are SUPERIOR features
contributing to its outstanding success for sound projection.

Manufactured by

HOLDING CORPORATION

COXSACKIE

COXSACKIE, N. Y., U. S. A.

loud .

clear

life-like

Type M-100

Dynamic Unit

5% by 5V„

31 West 21st St.

«>afs yV4 I l_ L S

NEW heights of reproducing power and
realism, based on years of intensive
research and development. Performance
that has won leading exhibitors interested
in attracting crowds into their theatres
. . . that will win YOU, by a single
trial. Get in touch with us at once!

MILES MANUFACTURING CORP.

'Builders of Acoustical Reproducers Since 1923"
(Phone GRAmercy 5081)

M 10 Horn

New York City

The Motion Picture Projectionist

November, 1929

Firmly Established as a Perfect Lens by Scientific Calculation, Precision
Work and Many Years Service in the Finest Motion Picture Theatres

SOLEX

PROJECTION LENS

Noted for High Illumination— Photo-
graphic Definition, Color Contrasts
and Perfect Focus

"As Easy to Put Together as It Is to
Take Apart"

Write for Descriptive Literature. It Will Be
Sent to You Immediately.

Manufactured by

KOLLMORGEN OPTICAL CORP.

767 Wythe Ave. Brooklyn, N. Y.

Your Preference, Please!

^pHE editors of THE MOTION PICTURE PROJECTION-
■*• 1ST solicit your aid to the end that this publication may be
of the maximum service to you. Every subscriber can do his bit
to improve this service by using the space provided below to
indicate his preference for special articles and other material in
which he may be particularly interested.

Let us know your preference, please. All requests will receive
attention in the order of their receipt, so act quickly. Use the
blank below to tell us in just what subject you are particularly-
interested. Do it now!

Editor,

M. P. PROJECTIONIST:

I am interested in the following subjects, on which I should
like to see information in THE MOTION PICTURE PROJEC-
TIONIST:

3. ;

NAME

ADDRESS

Subscribe NOW!— At present low rate of
$2.00 per Year

Keep Abreast of New Developments in Your Craft

Index of Advertisers

Argco Laboratories, Inc.

Bausch & Lomb Optical Co 45

Best Devices Co 5

Bioscope, The 6

Blue Seal Products Co., Inc 9

Brenker Lt. Projec. Co 42

R. C. Burt Scientific Labs 34

Canadian Theatre Supply Co 35

Chalmers Publishing Co 39

Clarostat Manufacturing Co 49

Coxsackie Holding Corp 49

Dowser Manufacturing Co 8

Eastman Kodak Co 41

Enterprise Optical Mfg. Co Cover

Essannay Elec. Mfg. Co 17

Fish-Schurman Corp 42

Forest Electric Corp 6

E. E. Fulton Co 14

General Machine Co 44

Griffin Manufacturing Co 34

Griswold Machine Works 45

Hall & Connolly, Inc 6

Hertner Electric Co 40

Hoffman & Soons, Inc 46

Ilex Optical Co Cover

Imperial Electric Co 35

International Projector Corp 10

Sam Kaplan Mfg. & Supp. Co 2

Kollmorgen Optical Co 50

Macy Manufacturing Co 39

Henry Mestrum 6

Miles Manufacturing Co 49

Monarch Theatre Supply Co 48

National Carbon Co 5

National Theatre Supply Co 7

Oliver Manufacturing Co 48

Pacent Reproducer Corp 3

Projection Optics Co 46

Raven Screen Corp 37

R. C. A. Photophone, Inc 26-7

Hugo Reisinger, Inc 9

J. M. Rice & Co 48

Roth Bros. & Co 44

Sentry Safety Control Corp 51

Southwest Thea. Equip. Co 48

Strong Electric Co 43

Walker Screen Co 36

Weber Machine Co 38

Western Electric Co 13

Maurice Workstel, Inc 8

United Electric Co., Ltd 48

Dpco Products Corp 37

YOU'RE NOT
SUPPOSED TO
BE A FIREMAN

BUT

When Sire leaps out in the
booth you are the only one
to Sight the red menace—

Your burns may be slight or
again they may be mighty
serious

Whatever clanger occurs you
must Sace it Sirst and alone—

The wise projectionist boosts

SENTRY SAFETY CONTROL

REMEMBER

YOUR JOB IS TOO IMPORTANT TO WORRY ABOUT FIRE

MODEL }* i|*r

TAMES f 1 I* \\ I TOE

, Tif' II in V 1 «»

^^g[ H^^

MOTIOGRAPH DELUXE,
BUILT FOR THE HEAVY
DUTY REQUIREMENTS

OF SOUND PROJECTION

THE ONLY PROJECTOR
THAT TAKES THE

HEAT OFF THE FILM

THE ENTERPRISE OPTICAL MFG. CO.

564 W. RANDOLPH ST. CHICAGO, ILL.

'■ -\:r

in;

THE MOTION PICTURE

THE LENS THAT PUTS PERFECTION IN PROJECTION

THE ILEX
F:2.5

PROJECTION
LENS

Combines Maximum Optical and
Mechanical Efticiency

Its optical superiority is accepted and decisively proven under com-
parative test — by its greater brilliance, greater sharpness and greater
detailed definition.

These qualities, augmented by the adjustable mechanism — a noteworthy
achievement — overcoming entirely unsightly slopover or incomplete
covering definitely estabhshes Ilex leadership.

The Ilex equipped theatre provides for its patrons greatly improved
screening, thereby adding immeasurably to their enjoyment of the film.
Acquaint yourself with the details and the remarkable performance of
this Ilex F:2.5 Projection Lens. Write vis today.

ILEX OPTICAL COMPANY

ROCHESTER (Established 191©) NEW YORK

Sign of Perfection

SURE -FIT I

for
SIMPLEX PROJECTORS

Ready for quick deliv-
ery to all parts of
United States and
Canada

KAPLAN PROJECTORS

Suitable for
Vitaphone — Movietone

and all other sound

systems

Manufactured

and

Distributed

by the

Sam Kaplan

Manufacturing and

Supply Co., Inc.

At Last— The Perfect reel

The most troublesome factor of the projection room — the
need for a precision reel — is now solved for all time. It has
everything you have been asking for:

1st — Broken parts replaced by sections — all you
need is a screw driver and a few seconds of
time.

2nd — Saves money. You don't have to buy a com-
plete reel if you break a section.

3rd — Runs easily and smoothly. Absolutely no
friction. Saves wear and tear of film.

4th — Original in conception and design. A new
idea in reel construction.

Now Being Used by Thousands of Theatres and
Recommended by Expert Projectionists Everywhere

Sam Kaplan Manufacturing and Supply Company, Inc.

729 Seventh Avenue NEW YORK CITY

December, 1929
Vol. 3, No. 2

Published monthly by Mancall Publishing Corp.. 45 West 45th St.. A'. 1". City. Entered as

second class matter' Oct. 25, 1927, at Post Office, Nezv York. A". 1"., under the act of

March 3. IS/9.

Canadian Representative: H. N. Elliott, Suite 11, 27 Sherwood Ave., Toronto, Canada

25c per copy
$2.00 a year

December, 1929

The Motion Picture Projectionist

MEET THE

SENATOR

PRICE

00 Per

= Set

COMPLETE
with all necessary
conduit and wiring.

Combination

Change-over and Heat Shield

A. C. OR D. C. CURRENT

DOUBLE

BEARING

SHUTTER

SENCO
SPECIAL
COOLING
PLATE

FOOT

SWITCH

INSTALLED DIRECTLY OVER APERTURE

The most efficient change-over ever designed-
Built like a watch—It is compact, noiseless and
lightning fast.

Made specifically for sound equipment— Tested
and endorsed by Fox— Stanley— Poli Circuits-
Lower in price than any other.

Made and Guaranteed by

Sentry Safety Control

13th and Cherry
PHILADELPHIA

1560 Broadway
NEW YORK

The Motion Picture Projectionist

December, 1 929

FROM

BROADWAY

BARABOO

'ROJECTIONISTS in the most
sophisticated city in the world — and
projectionists in one of the smallest
townships in the country have pur-
chased Miehling's definitive book on
the thrilling subject of sound projec-
tion.

FF the presses and in the mails —
the first edition of this remarkable
volume is now streaming east, west,
north and south to thousands of pro-
jectionists who ordered and paid for the
book in advance of publication, sight
unseen. This is a fine tribute to author
and publisher, a confidence based on
past performance.

\_J NLY a few hundred books are left.
Order your copy now for immediate
shipment.

▼ Y EIGHS two pounds — worth its-
weight in gold.

PRICE $6^

We Pay
Postage

ORDER NOW

THE MOTION PICTURE PROJECTIONIST

45 West 45th Street, New York City
Gentlemen:

Please send me Rudolph Miehling's book.
"Sound Projection." Enclosed find check (or
money order) for $6.00.

Name

Street -

Town -

State

December, 1929

The Motion Picture Projectionist

"Sovereigns of Sound"

THE motion picture operator once was
just the man who turned the crank.
Now he is an! artist, a sovereign of sound,
the master of talkie fate. These "pro-
jectionists," as they are called, do not,
however, give themselves those lordly
titles. Though they manipulate the lime-
light, they keep out of it themselves. They
do not speak like Hollywood stars of "my
public." They subordinate themselves to
their exacting technique by calling them-
selves projectionists.

They are indeed engineers, for they
manage a very complicated piece of mech-
anism. But they are more than mechanics.
It is said of them that even though they
be good electricians, well-versed in the
laws of optics and acoustics, as dexter-
ous in doctoring their machine in full
flight as an aeroplane mechanic who crawls
out on a wing and repairs his machine in
full flight, all these virtues are nothing" if
they have no sense of the theatre, if they
are not stage managers and showmen.

The Marvelous Duo

I watched two projectionists in action
in a big Toronto sound picture house. I
had to go to the very roof of the theatre
and then climb other stairs to a super-
roof. It gave me the feeling of climbing
to the crow's nest of a ship. They were
indeed like look-outs keeping watch in
foggy weather. From their peep-hole they
kept their eyes steadily fixed on the screen
far below them and were ready to spring
to a switch or a lever at the least sign of
visual or auditory deficiency. — Toronto Star
Weekly Magazine.

7,000 Show Musicians Idle

More than 7,000 out of a total of 25,000
members of the American Federation of
Musicians who were formerly employed in
theatre work are now out of work, accord-
ing to official figures issued from the national
headquarters of that organization. No secret
is being made of the unrelenting opposition
of Federation officials and members to the
"talkies," as they term them, and a spirited
advertising campaign, estimated to exceed
a cost of more than $250,000, is now in
progress to acquaint the American people
with the dangers of "flat, savorless, me-
chanical music."

President Weber's Statement

In a recent statement President Joseph
Weber of the Federation said : "A great
cultural calamity awaits the United States
if its citizens allow one industry to force
it into an acceptance of flat, savorless,
mechanical music." Weber also cites many
letters and telegrams which have been re-
ceived from all over the country as evi-
' dence that the Federation has the moral
support of many thousands in its fight
against sound pictures.

Dissension and lack of harmony handi-
cap the trade union, but co-operation and
the union label solidify it.

Photo by Apeda, New York

BRING THEM BACK FOR MORE

WITH National Projector
Carbons behind your films
you can be sure of a good
showing. Clear projection
brings satisfaction. The mod-
ern soft, low key or fuzzy
film, shot with trick angles or
light-absorbing prisms, re-
quires greater illumination to
get the effect on the screen
. . . that means stepping up the
amperage. National Projector

Carbons burn smoothly on
increased amperage . . . pro-
duce greater light without
spitting or pitting. This in-
sures clear, flickerless pic-
tures — pictures that please
the audience and are easy to
look at. With good films and
good projection your theater
will stay crowded. National
Carbons help keep attendance
growing.

National Projector Carbons

NATIONAL CARBON COMPANY,
Carbon Sales Division, Cleveland, Ohio

Unit of Union Carbide Ik ^ and Carbon Corporation

INC

Branch Sales Offices: New York, N. Y.; Pittsburgh, Pa.; Chicago, 111.;
San Francisco, Calif.; Birmingham, Ala.

IN WESTERN CANADA!

CANADIAN THEATRE SUPPLY CO.

Authorized distributors for

SIMPLEX— MOTIOGRAPH— POWERS— HOLMES

and all theatre equipment of the leading manufacturers. Also, an extensive line of

stage equipment.

Complete Sound Picture Service!

105 Capitol Theatre Building

Winnipeg, Man., Canada

Alberta Representative

M. L. ADAMSON
1605 — 104th St., Edmonton, Alb., Canada

The Motion Picture Projectionist

December, 1929

TRUVISION

NATURAL
VISION

PROJECTION

SCREEN

Perforated Glass-Bead Screen

(Pat. Pdg.)

for Talking Pictures

Brilliance — Depth — Definition —
Third Dimension Illusion

Electrical Testing Laboratory Report
47766, Sept. 11th, 1929

Fox's Blenheim Theatre installs Truvision
Perforated Glass Beaded Screen for sound
pictures replacing the former sound screen.

Photophone R. C. A.

RADIO CORPORATION OF AMERICA,

GRAMERCY STUDIO, N. Y., USES

THE TRUVISION SCREEN

50 ft. x 30 ft.

The Biggest in the World

TRUVISION TALKIE SCREEN IS
THE LAST WORD FOR PRO-
JECTION AND FOR SOUND

Truvision Projection
Screen Corporation

841 Tiffany Street, Bronx, N. Y.

PHONE: DAYTON \ |||^

Get the Facts

About the new 1930

TALKING PICTURE

SOUND
EQUIPMENT

Amplion sound equipment is designed to a standard
and not to a price, with the result that marvelous qual-
ity and great volume are realized.

Amplion builds MATCHED theatre sound equipment
and group address systems to fit any requirement and
with 43 years success in this field Amplion engineers
are prepared to cope with any acoustical situation. Your
correspondence is cordially invited.

Investigate Before You Buy
SAVE RUINOUS EXPENSE

AMPLION

is the one place in America
where you can purchase a com-
plete eqi
desired.

Amplion Exponential 10 ft. Air

Co.umn Ho.n
Specially designed to reproduce the
human voice and orchestral music in
talking picture and group address in-
stallations.

Amplion Giant Dynamic Air Column
Unit

Through new design we perfected a
new unit with a stronger magnetic fhld;
also, due to a revolutionized internal
construction, 300% greater volume is
delivered at the 5,000 cycle note than
before. Th<"se high frequencies make
possible quality reproduction heretofore
unattainable.

Amplion Disc Synchronizing Machine

Amplion Synchronizer delivers a con-
stant, fixed spe d. Motor drives both
projector and turntable. Coupled to
the projector by a silent chain drive
that eliminates vibration to the turn-
table. Located on right hand front
side of projector — thus saving spac> in
projection room.

Theatre Power Amplifiers — Exciters

2 and 3 Stage Power Amplifiers

Microphone Input Amplifiers — Faders

Magnetic and Dynamic Cone Speakers, etc.

Catalog on Request

Amplion Corporation of America
133-141 West 21st Street New York, N. Y.

December, 1929

The Motion Picture Projectionist

TeamworK

Perfect Projection is de-
pendent upon a number of
factors aside from the Pro-
jector itself, and also upon
TEAMWORK between these
factors.

Current supply is probably
the most important of these.
This must be absolutely de-
pendable at all times if high
quality projection is to be
expected.

PROJECTOR RHEOSTAT WITH
ARC-STRIKING SECTION

FULCO PROJECTOR

We have special
literature telling all
about this fine set
and we would like
to place a cop}' of
this in your hands.

General Electric engineers
have produced for us a motor
generator that is just what
you will want if your current
supply is A.C.

We just want to say here
and now that with this new
G. E. Motor Generator set on
the .job, you can always be
sure of Effective Teamwork
between current supply and
Projector.

GENERATOR PANEL

G.E. Induction Motor Generator Set Rated 20/40 Amp. 80/80 V.

We can't begin
to tell you in this
space all the inter-
esting facts about
it. Send for litera-
ture.

Made Exclusively for and Distributed Solely by

E. E. FULTON COMPANY

Executive Headquarters — 1€18 So. Wabash Ave.

CHICAGO

O*4

*N°V

President
C. H. FULTON

Treasurer
A. G. JARMIN

BRANCHES

CHICAGO — 1018 So. Wabash Ave. ST. LOUIS — 3232 Olive St.

NEW YORK — 115 W. 45th St. INDIANAPOLIS — 340 N. Illinois St.

BOSTON— 65 Broadway MILWAUKEE — 151 Seventh St.

PHILADELPHIA — 1337 Vine St. SAN FRANCISCO — 255 Golden Gate Ave

ATLANTA— 146 Walton St. LOS ANGELES— Film Ex. Bldg.

Factory: 2001 So. California Ave., Chicago, 111.

V. P. & Sales Mgr.
F. A. VAN HUSAN

cA<^ •••■'

^F <f (p ^

The Motion Picture Projectionist

ecember,

1929

DON'T BIAME THf BOOTH

FOR THE BACKTALK
OF YOUR TALKIES /

Nine times out of ten — providing sound equip-
ment is good — unsatisfactory talkies are the
result of poor acoustics. In these days of per-
fected talking pictures the public is rapidly getting
more and more insistent on clear, distinct voices.

The problem of getting good acoustics in the
average theatre, fundamental as it is, is fortu-
nately not as great as it might appear to the
average exhibitor.

Expanses of hard echoing surfaces — alcoves and
sound pockets — responsible for most of the echo.
The veneer seats replaced with upholstered chairs,
draperies scientifically hung, and floor spaces
properly carpeted will go a long way toward the
complete elimination of echoes, and poor sound
distribution in your theatre.

National Theatre Supply Company's Acoustical
Experts will gladly cooperate with you in a solu-
tion of this problem.

Write today, for further information on
materials, prices and terms

Maybell & Leona

The Exhibitors Own
Song and Chatter Team

"You'd 'a'

thought you was at a Sunday School Picnic"

"Well, Maybell, I went like you told me and
saw the pichure that you was ravin' to me about
and, believe me, saw it is exactly what I done. I
gotta go back again if I want to hear it. We was
late to begin with, and hadta perch way up among
the chandeliers and any time anybody said some-
thin' in the pichure, why it sounded up there like
about sixteen old maids at a tea. They was echoes
or somethin' all over the place and so, with all
this clatter that didn't mean nothin', and Paddy
decidin' to get amorous, you woulda thought we
was at a Sunday School picnic.

"So Paddy says, when we got outa the place.

'Pretty good sho, wasn't it, kid?' and I says, 'I'll bite,
was it?' (How should I know if the show was good
if I couldn't hear what it said?) 'Listen, sap,' I says,
'I know my talkies and where to go to hear 'em.'
'"Oh, is zat so?' he says. 'Poisonally, I tought it
was a swell pichure.'

'"Oh, yeah', I says, 'well you would because in
the first place, if I got any memory a tall, your
mind wasn't at no time on the pichure, and fur-
thermore,' I says, 'don't never ask me to come
back here to take in another of your swell talkies
in the silent. I simply gotta take my art straight
or not a tall."'

NATIONAL THEATRE SUPPLY COMPANY

624 South Michigan Avenue, Chicago Branches in All Principal Cities

December, 1929

The Motion Picture Projectionist

The Invisible, Noiseless Changeover for SIMPLEX— MOTIOGRAPH F.— SURE FIT

HOLMES— SUPERIOR Projectors

Also for the New Super Simplex

AUTOMATIC SHUTTER CONTROL

and

3-WIRE CIRCUIT
FOOT SWITCH

(Miniature power house)

Switch floor brackets
now available

Designed for the simplest

installation and changeover

dependability with all sound

equipment.

Ask your dealer or write

DOWSER MANUFACTURING CORP.

691 Lincoln Place, Brooklyn, N. Y.

Telephone: Prospect 2049

Installed by
Roxy — Keith — Stanley — Schwartz
Loew— Fox — Wilmer & Vincent

JUST OFF THE PRESS

Our slides used with the
BRENKERT F-7 Master
Brenograph.

One of these valuable
catalogs will be sent to
you immediately if you
will write to us.

This catalog is an important contribution
to projection technique. You will be behind
the times unless you keep yourself posted on
these presentation effects.

WORKSTEL STUDIOS

151 WEST 46TH STREET

NEW YORK CITY

The Motion Picture Projectionist

December, 1 929

He Was Mistaken/

Are You?

"No, Ma'am, we don't have any
talkies in this theatre."

"What! No talkies? Only silent
pictures?"

"Yes, Ma'am. You see, it costs so
much money to install the talking
equipment — "

"Well, that's just too bad, but I'm
going to a theatre that has talkies."

— and that's just what she — and
millions of others are doing.

AVCIE LOSING BUSINESS

By Installing

syNCRCDisr

SYNCHRONIZED TURN TABLES

HIGH
POINTS:-

Spring Suspension: The
Syncrodisk patent that spells
steady even motion. The
secret of fine talkies.

Metal Guard surrounding
the disk has two pockets for
needles. Not Driven Off
Intermittent.

Installation: Can be made

by any operator and wire

man. In one hour you are

ready to run the standard

16" synchronized disks.

Comes Complete with

two pick-ups and

change-over fader.

More Than 400 now
performing smoothly
every day.

When your patrons ask you when you are
going to give them talking pictures what answer
will you make? Get in step with modern prog'
ress and give the people talking pictures. Install
the machine which is quality personified — built
by Weber whose tradition is precision — the only
Turn Table with Spring Suspension. Install
two Syncrodisks for the small sum of $500 and
watch the increase in business.

COMPLETE $PAA
for only.. tJVv

HENRY A. LUBE, European Distributor
118 Blvd. Haussmann, Paris, France

RADIO MOTION PICTURE CO.

156 W. 44th St., New York.

Write, Wire or Phone Glenwood 6520

Weber Machine Corp.

59 RUTTER ST.

ROCHESTER, N. Y.

ecember,

1929

The Motion Picture Projectionist

Equipment Troubles and Maintenance

By C. R. Travis

LAST month we discussed ways and
means of tracing trouble to one of
the four major portions of the
sound reproducing system. In this install-
ment we shall resume where we left off,
which was, as you remember, with the
assumption that the trouble was to be
found in the reproducer portion of the
equipment. From this point we shall pro-
ceed to make a final analysis and clear the
trouble.

Disc reproducers or magnetic pick-ups
ordinarily will give little trouble, unless,
of course, they are subjected to improper
handling. The attendant circuit is a simple
one. It consists merely of a pair of wires
leading from binding posts on the repro-
ducer through the tone arm and to a
knockout box located or. the front wall of
the projection room. From this latter point
connection is made direct to the fader bind-
ing posts corresponding to that particular
circuit. Any trouble which is located be-
tween the pick-up and the fader may be
readily located by means of earphones, as
described in the last issue.

In one of the major companies' instal-
lations, however, this circuit takes a some-
what different path. The circuit leaves the
reproducer and follows the reproducer arm
to the swivel bearing, passes through the
tone arm and there enters conduit, from
where it is lead through a connection box
adjacent to the amplifier panel and then into
an equalizer panel mounted on the amplifier
rack. The circuit then leaves the equalizer
panel, returns through the connection box
and goes to the fader terminal posts. The
equalizer is for the purpose of flattening
the characteristics of the reproducer and
probably would never give any trouble.

Other Reproducer Troubles

Perhaps the most common trouble with
disc reproducers is the jumping of the
record groove by the needle ; this and the
problem of maintaining synchronism are the
usual faults of reproducers. Both these
faults may be the result of one or a com-
bination of causes. A listing of these
troubles in the order in which most com-
plaints are made follows :

1. Vibration in the turntable.

2. Poor records.

3. Tightness at the swivel bearing.

4. Improper reproducer drift.

5. Needle not meeting the record at the
proper angle.

•* ^-\ PIVOT

5HIV£L 0f»/»ffC

•-^ PIVOT

?omr 6 OZ.

Tone arm with vertical adjustment at end

6. Improper handling — rough usage.

7. Insufficient mass in the reproducer and
reproducer arm assemblies to hold the
needle in the record groove.

8. Too high a mechanical impedance in
the reproducer.

9. Turntable not level.

10. Use of incorrect needles.

Turntable Troubles

Turntable troubles usually are the re-
sult of improper alignment of the table
with respect to the projector or its driving
element. The turntable must set level, and
the center of the drive shaft of the turn-
table gear pot must be in the same plane
at all angles with the center of the driving
shaft. To obtain these conditions proceed

Cross-Section of a Record

Any average reproducer will follow grooves
1, 2, and 3. Only a well-designed assembly
will follow 4 without breaking into 3 or 5.
Only a perfectly adjusted assembly will
follow 5 or 6 without jumping.

as follows : Disconnect the driving mech-
anism from the turntable gear pot and
carefuly level the table by means of the
leveling screws at the base of the pedestal.
Raise or lower the pedestal in its base
until the column is approximately at the
level required to bring the two drive shafts
to the same height. Complete this adjust-
ment by means of the leveling screws.

Turning all of the leveling screws an
equal amount will not affect the level of
the turntable. Move the base of the turn-
table until the two shafts line up in a
straight line. This procedure must be re-
peated until perfect alignment is attained.
The tools required are a crescent wrench,
a level about 8" long, and not a little of
that virtue known as patience.

In projection rooms having linoleum
floors or rubber pads in under the turn-
table legs there is need for a daily adjust-
ment for about a week after the leveling-
off process, to check up on any compression
of either linoleum or rubber. After the
turntable has apparently settled permanenly
to such flooring it is advisable to check
weekly so that there may be no shifting.

The coupling device usually consists of
a rod of some type connected to the driving
and driven shafts by means of rubber con-
nectors. These connectors should neither
be compressed nor stretched under opera-
ting conditions, and every effort should be
made to remove the wobble inherent in this
type of coupling. Usually a wobble in
these couplings indicates that the shafts

are not properly aligned or that the cou-
pling is being compressed. It will be found
that if this set-up is rigidly adhered to,
turntable vibration will be practically
eliminated.

Poor Records

A reproducer that jumps at one parti-
cular spot on the same or like records
is generally not at fault, unless it is noted
that this happens altogether too often with
various sets of records. When this con-
dition is encountered the records should be
examined carefully with a good grade of
magnifying glass. If the grooves appear to
run together and the side wall between the
two grooves has the appearance of being
overcut, it is safe to assume that the re-
producers are functioning satisfactorily.

Tightness at Swivel Bearing

A reproducer which jumps at the same
physical location irrespective of the record
shows that it is being held from tracking
by its bearing or some outside cause ; and
the reproducer arm swivel bearing should
be inspected at once. If the tightness can-
not be located, change the entire reproducer
arm. A typical case in point is one where
the cords leading through this bearing had
become twisted and were exerting back
pressure enough on the reproducer to cause
it to jump.

Either of these conditions can be recog-
nized by taking the reproducer in one hand
and gently swinging it through the path
it normally follows. Any tendancy to stick
on the part of the reproducer will show that
the arm is not working satisfactorily.

Improper Reproducer Drift

By "drift" of a reproducer is meant the
tendancy to swing to either one side or
the other with respect to the top of the
. turntable. The generally accepted theory
is that the "drift" should be such that the
reproducer, when given a slight jar, should
start from the center of the turntable and
move toward the outer edge in its normal
direction of travel, slowly and without
further urging. This test may be made
by either counter-balancing the weight of
the reproducer on the tone arm by placing
a wrench or other object at the back end;
or in the case where the vertical movement
of the reproducer is provided for at the
reproducer, by fastening it up and back
against the arm. If the drift is not correct,
adjustment should be made.

At the top of nearly all pedestal tone
arm brackets there is a platform in which

r VEtrricflL pivot

- 5YTIVEL BEARING

Yf6T. AT rVKOtf
POINT 6 OZ-.

Tone arm with reproducer firmly attached

The Motion Picture Projectionist

December, 1929

the tone arm assembly sits. This platform
can be tilted to give the reproducer arm
the required drift. The entire assembly
should be raised or lowered on the pedestal
to make the reproducer arm level when the
reproducer is in its operating position. Be
sure that the lock rings are tight against
the felt and that there is no motion in the
pedestal tone arm bracket before okaying
the adjustment.

Proper Needle Angle

The needle must be vertical on the record
as seen from the front of the reproducer.
If it is off even slightly it will not ride
the record groove properly and will jump
frequently. The reproducer can usually be
rotated sufficiently in the arm to correct
errors of this type. Looking from the
side of the reproducer, the needle should
meet the record at an angle of between
65 and 85 degrees.

Dropping a reproducer onto the record
or turntable will sometimes bend the arma-
ture and cause the reproducer to induce a
rattling or blasting sound in the speakers.
This condition should not be confused with
the perfectly normal noise that is made
when running through heavy music cuts on
the record. Manufacturers recommend that
defective reproducers be returned to them
for repairs, and projectionists should not be
slow to avail themselves of this opportunity
to replace defective equipment.

Insufficient Reproducer Mass

Some makes of reproducers are too light
for the work assigned to them. This state-
ment must not be confused with the weight
of the needle upon the record, which is
an altogether different matter. Ideal re-

producer weight has been generally stand-
ardized at between 4 and 6 ounces, as with
less weight there is a tendency to jump
the groove; while excess weight damages
the record to the extent of making it
worthless after a few playings.

The reproducer should have sufficient
mass so that it will not be thrown by the
action of the needle as it endeavors to fol-
low the grooves of the record, particularly
on heavy bass notes. In cases where the re-
producer is fastened solidly to the tone
arm, and the vertical motion is obtained
by a bearing at some point along the tone
arm, it is easy enough to add weight to
both sides of this bearing to make mass
and prevent the reproducer from being
thrown. In doing this be sure that the
weights are so distributed that the pres-
sure of the needle on the record is not in
excess of 6 ounces. There is nothing that
can be done with reproducers that are
hinged to the tone arm to allow for ver-
tical motion.

High Mechanical Impedance

High mechanical impedance results from
an armature so rigid that it does not allow
the needle, to follow the groove, and in the
case of an assembly having a large mass,
simply pulls the needle through the groove ;
or, in the case of a light mass, allows the
needle to throw the reproducer. Either
case will cause the reproducer to jump
or ruin the record by breaking down the
side walls of the grooves.

Correct needles are specified by the manu-
facturers of the various sound picture
equipments, and it is always a good prac-
tice to follow these recommendations ex-
plicity in order to secure the best results.
(To be Continued)

Why 1,000-Foot Reels?

EXPERIENCE has taught film pro-
ducers that the use of single, or 1,000-
foot, reels with sound-on-film subjects is
conducive to bad prints and poor presen-
tation of sound pictures. Most of the
leading film producers have adopted the
practice of shipping sound-on-film subjects
on 2,000-foot reels, thus making it un-
necessary for the projectionist to delete
any sections of film for the purpose of
joining up two short reels. However,
there are still a few producers who ad-
here to the old custom of shipping on
single reels, and this practice has done
much to mar the presentation of many
sound pictures.

The evils attendant upon the continued
use of 1,000-foot reels are admirably set
forth in the following communication from
a Local Union Secretary, whose Local
members have experienced much difficulty
in properly presenting sound film subjects.
Most of the disadvantages of short reels
are set forth in this letter, and those
which are not stressed are too well known
to projectionists to need further com-
ment here. The letter follows :

We would like to have vou take up with
the producers of Fox Movietone feature
pictures the matter of their putting- out
their multiple reel subjects on 2,000-foot
reels instead of on 1,000-foot reels, as at
present. No one runs either silent or
sound-on-film subjects on single reels, no

matter how they are shipped from the
exchange, and all such reels are doubled
up into approximately 2,000-foot subjects
before they are run.

Render Cue Sheets Worthless

As these subjects come on single reels,
they must be cut again after using, so that
they may be sent out on the original ship-
ping reels. This means 2 cuts on the end
of every odd-numbered reel and 2 cuts on
the start of each even-numbered reel in
each theatre where the subject is shown.
We have reason to believe that even here
where all our projectionists are first-class
men, careful and conscientious, this_ con-
tinual cutting does not help the picture
any. Due to censor cuts, etc., some reels
are very short, while other reels are filled.
When separating such reels after they have
been doubled up the tendency is to even up,
or balance, the footage on each small reel.
This means that after the first run the
original cue sheets_ are worthless.

In doubling up, in order to have a con-
tinuous picture on the screen, the cut is
made at the last picture frame on the one
reel and at the first frame on the next, ex-
cept in cases of a fade-in or fade-out. In
some cases the sound record runs on past
the last picture frame, and then we are
faced with the choice of cutting off that
stretch of sound record (perhaps dialogue),
or having our screen go dark while the
sound is permitted to run. In cases where
the sound runs right up to the last frame,
or starts with the first picture frame, quite
a bit of sound and picture are missing by

the time the print has been around to a
few theatres — because every time the single
reels are doubled up and separated a full
picture frame and its accompanying sound
record are lost.

Audience Reaction

We all know that there are many good
reasons why all sound-on-film subjects
should be sent out on 2,000-foot reels, and
a number of companies are doing this with
both features and comedies. I earnestly
request that you take up this matter with
those companies not now using 2,000-foot
reels and thereby render a great service to
all branches of the industry.

We projectionists have no interest in
view in pointing out these little defects in
the sound picture scheme other than to ren-
der the whole industry a service. The
splicing together of short reels means very
little in our daily routine, yet it simply
doesn't set right with us when we see good
feature pictures, costing many thousands
of dollars to make, being marred con-
stantly by the small matter of larger reels.
Such things do not please the picturegoer,
and I believe this is the purpose of all of
us in the industry.

F. P. Broadbent,
Secretary Local 360,
Edmonton, Alb., Canada.

The Perfect Speaker

WHAT would be the characteristics
of a perfect loud speaker? In the
first place, a perfect loud speaker would
reproduce all the frequencies over the en-
tire audio-frequency band which extends
from say 15 cycles up to about 12,000 to
14,000 cycles. It would reproduce all these
frequencies without discrimination, in other
words, a response curve of its performance
would be "flat" over the entire band. The
perfect speaker would introduce no new
frequencies ; that is, if supplied with a
pure 60-cycle current it would produce a
pure 60-cycle note and not a complicated
tone consisting of some 60 cycles and also
some of the harmonies of 60 cycles.

It would be capable of handling the
maximum desired volume without distor-
tion due to overloading or rattling. It
would be efficient, converting all or nearly
all of the electrical energy supplied to it
into sound. It would have a very long
useful life and be not in the least affected
by dampness or other atmospheric condi-
tions.

Audio Frequency Range

The problem is how far the practical
speaker can depart from the ideal and
still be satisfactory. The range of audio
frequencies extends from about 15 to
14,000 cycles, but the problem is to decide
how many of the low frequencies and how
many of the high frequencies can be
eliminated before serious distortion results.

Competent authorities feel that essen-
tially perfect reproduction can be obtained
in the frequency band between 30 and
10,000 cycles, the elimination of all fre-
quencies above and below these limits
causing no noticeable change in quality.
Further it has been found that cutting the
frequency band from 10,000 down to 6,000
or 7,000 cycles produces but a very slight
change in quality — a change that can only
be detected by a direct comparison be-
tween the original and the reproduction.

ecember,

1929

The Motion Picture Projectionist

THE FOURTH OF

SERIES ON QUALITY REPRODUCTION

WESTERN ELECTRIC

The Voice is

a Precious Cargo- *uarded

^y from actor to
audience through a great chain of men and apparatus so that
when it reaches the loud speaker it shall be true and faithful.

If the loud speaker fails to operate efficiently, even the
best pictures will not "click."

That this final link shall not fail, the Western Electric
Sound System uses the horn speaker — developed by the Bell
Telephone Laboratories — backed by over 50 years of research
and experience — a direct descendent of the first telephone
receiver invented by Alexander Graham Bell!

he Western Electric
Horn Speaker delivers u ten times

as Efficiently as any other

IT requires just one tenth the amplification
to produce the desired volume without
distortion.

It comes nearest to reproducing the entire
range of music and voice — over -emphasizing
none of the notes. It does not play up the low
notes by sacrificing the high. These high notes
are essential to quality sound reproduction, to
preserve the color, charm and individuality of
the actor's voice.

Its directional effect creates the perfect
illusion that the voice comes from the lips of
the actor on the screen. With speakers that
lack direction, illusion is lost.

It is designed especially to direct the sound
to all parts of the theatre in equal volume,
bringing words and music clearly to every
person in the house, and overcoming many
acoustic faults. With speakers lacking direc-
tional effect this is impossible.

The Horn Speaker Contributes to Quality in the

Westen

SOU ND

%Eteetric

SYSTEM

Distributed by

Electrical Research Products Inc.

250 West 57th Street, New ^ork, N. Y.

Member of Motion Picture Producers and Distributors of America, luc Will H. Hays, President

The Motion Picture Projectionist

December, 1929

E MAR* REG'C

THE INTERNATIONAL PROJECTOR

PROJECTION

an Important Pan of Good SKi-^-ir

yHE MOTION PICTURE PROJECTOR
is no longer a mere mechanical contriv-
ance, cranked by hand, or made to
operate by the simple closing of a switch.
The Projectionist of Today must have an
excellent knowledge of mechanics, electricity
and optics and is in charge of a delicate and
complicated mechanism made with scien-
tific accuracy to handle a fragile and in-
flammable material.

HE PROJECTIONIST has a great respon-
sibility— for a failure to measure up to the
right standards means that all the producer;
director, actor and cinematographer have
striven for loses much of its artistic and
commercial value, — the pleasure of the
audience is lessened, — the exhibitor is sub-
ject to constant and unnecessary expense,
— and lives and property are endangered.

INTERNATIONAL PROJECTOR CORPORATION
90 GOLD STREET, NEW YORK, N. Y.

BfflSMaiBMrWMSWaTWfflvW^

JLhis advertisement
first published eight
years ago is re -published
by request.

Supremacy

IS BASED UPON A THOR-
OUGH UNDERSTANDING OF
THE REQUIREMENTS OF
MODERN PROJECTION.

THE INTERNATIONAL PROJECTOR

International Projector Corporation

90 GOLD STREET

NEW YORK

December, 1929

The Motion Picture Projectionist

Synchronizing Record Starts

By Arthur B. Reeves

The International Photographer, Hollywood

DURING my recent trip East I
visited many projection rooms.
While in New York City I visited
the projection rooms of the Paramount,
Roxy and Capital theatres, all Broadway
houses. In each instance I inspected the
sound equipment and asked the projection-
ist in charge many questions regarding
synchronization. I also discussed the rela-
tive difference between sound-on-film and
disc recordings. To my surprise many
projectionists stated that they get better
quality of tone reproduction from discs,
but in all cases they said that sound-on-
film is much easier to run and causes but
little trouble, comparatively.

The projectionists with whom I talked
regarding sound film breaks stated that
they have very little, if any, trouble with
film which has a sound-on-disc accompani-
ment. With disc accompaniments it has
been found that the starts are chewed up
by the sudden starting of the projection
machine, resulting very often in consider-
able trouble in placing the needle back
into the proper groove to insure synchroni-
zation.

Record and Projector Speed

While in Chicago I was in touch with
George Moore of Local 110, projectionist
at the Metropolitan Theatre in that city.
Together we worked out a method where-
by, when the leader of a sound-on-disc film
is broken off, it is possible to put the
needle in the proper synchronizing groove,
notwithstanding.

Now, let us consider the ratio between

Figure 1 — Regular Vitaphone record, with center panel numberings.

the record and the speed of the projector.
The projector runs 1440 pictures per
minute, and the record makes ZiYi revo-

Figure 2 — Center panel of Vitaphone disc with 43 equal divisions.

lutions per minute. When worked out, it
is found that there are 42.3 picture frames
to one revolution of the disc. You will
note in Figure 1 a regular Vitaphone
record with the starting mark. In Figure
2 you will note a regular Vitaphone record
with a scale dividing the record into 43
equal parts, beginning at the starting
mark. This scale does not, however, inter-
fere with any of the markings on the
record. It can be a part of the label or can
be stamped in the matrix when the record
is made. In Figure 2 you will also notice
a portion of the center label given over
to a scale which relates in various foot-
ages to the correct starting points.

Scale of. 43 Positions

For example, suppose we are making a
changeover from the fourth to the fifth
reel of a feature, and as we do so the
machine "chews up" a portion of the leader
(at the start) of reel five. The show is
interrupted, the theatre is dark and the
audience is waiting impatiently for the
resumption of the show. In the past it has
been necessary for the projectionist to take
the whole reel out, measure off the portion
of film that has been mutilated and add
a portion of equal length; then to re-thread
the projector and start off from the syn-
chronizing point. This operation requires
considerable time.

With the scale of the 43 positions upon
the record, however, the projectionist has

The Motion Picture Projectionist

December, 1929

o
a

22/t. wmN

a
a

■48 mm

a
o

□

a
a
a
o
a
a
a
a
a
a
a
a

a
a
a

a
a
a
a

<- }■ 35i«.vn 1 — ^

a
a
a

aivmn

Diagrammatic representation of new Fox Grandeur and standard film sizes.

but to look at the edge numbers which are
on the side of the film and which run con-
secutively from the start, to determine the
exact footage of the damaged film. For
example, let us say that the projector has
been re-threaded for five feet beyond the
starting point.

As we thread the projector we know that
we are exactly five feet from the starting
mark of the film. We now turn to the
record and note upon the scale printed
on the label that five feet of film requires
one turn and 38 frames. With the turn-
table stationary, we place the needle on the
starting mark. We turn the record, with
the needle in the groove, one turn and
around again to 37 upon the diai. We have
now attained perfect synchronization with
the film and we may start the projector.

This can all be accomplished so quickly
that the interruption is so brief as to pre-
clude any demonstration by the audience
of its feelings. As previously stated, it is
very seldom that the film breaks in the
middle of the reel, the bulk of trouble of
this nature being encountered at the start
when leader is mutilated.

Film Edge Numbers

All positive film is numbered along the
edge consecutively and these are known
as footage numbers. At every foot of film
a number appears, with the numbers run-
ning consecutively to the end of the reel.
Vitaphone subjects have a special number-
ing of their own, which may easily be dis-
tinguished from other markings. In the
foregoing example where it was assumed
that five feet of film had been "chewed up,"
suppose we should have threaded the pro-
jector at five feet and three frames. In this
case we would simply add the three frames
to the scale, and instead of one frame and
37 frames on the scale it would be one turn
and 40 frames. Therefore, no matter what
the footage, it will be simple to place the
needle in the proper synchronizing point.

The Footage Scale

Below is printed the scale which is used
for calculating the synchronization of disc

and film. Previously I quoted 43.2 picture
frames to one revolution of the disc, there-
fore we have divided the record into 43
equal parts. The .2 difference is compen-
sated for in this scale. This scale runs up
to 25 feet, but in cases beyond 25 feet it
is only necessary to add the additional to
the 25-foot requirements.

This method is protected by Edgar J.
Clarkson, patent attorney, 905 Victor
Building, Washington, D. C. The scale
follows :

Feet Turn Disc Frames

1 16

2 32

3 1 5

4 1 21

5 1 37

6 2 10

7 2 26

8 2 42

9 3 V.. .15

10...... 3 31

11 4 4

12 4 20

13 4 36

14 5 8

15 5 24

16 5 40

17 6 13

18 6 29

19 7 2

20 7 18

21 7 ..34

22 8... 7

23 ...8 23

24 8 39

25 9 12

The operation is simple. We will re-
peat the procedure. First determine the
amount of film that is missing. Thread
the machine according to the edge number,
then read the scale. Place the needle at
the starting point, and with the turntable
stationary, turn the record with the needle
in the groove the number of turns which
are indicated on the scale for that par-
ticular footage. The needle will thus be
in the proper groove to insure synchro-
nization.

More on Film Patches

THE following abstract from a paper
prepared by Messrs. Crabtree and
Ives of the Kodak Research Laboratories
and read at the recent meeting of the
S. M. P. E. at Toronto, is interesting in
connection with the material on new film
patches which appeared in these columns
last month :

When two pieces of motion picture
film bearing photographic sound records
are spliced together end to end, an ir-
regularity in the opacity is introduced at
the point of junction. This irregularity
is abrupt and causes a sudden change in
the light transmitted by the film passing
the light sensitive element of the sound
reproducing device. Therefore unless
some means is utilized for gradually
masking off the entire width of the sound
record in the vicinity of the splice, a
foreign noise is heard when this part
of the record is reproduced in a theatre.

One means of masking this area is
by applying ink or black lacquer to the
film with a brush in a triangular area
covering at its widest part the splice in
the sound film record. This brush work
is slow and difficult to accomplish and
the results obtained are often unsatis-
factory.

A much simpler and quicker method of
rendering the required area opaque has
been devised. A patch made of thin
black film is cut to the desired shape and
perforated on one edge similarly to mo-
tion picture film for exact registration by
means of a small mounting block. With
a quantity of these patches on hand, the
projectionist is able to repair quickly a
broken sound) record or to join two such
films without introducing any noise into
the record.

Under the heading "Film Patches" there
appeared in the November issue of The
Motion Picture Projectionist a refer-
ence to a suggestion of A. Caminetsky
of Brooklyn, N. Y., for a new method of
sound film patching. Mr. Caminetsky
recommended the use of a gummed piece
of paper of exactly the same size as the
usual sound film patch. This method un-
doubtedly would eliminate any click as the
film passed the aperture ; but the objection
to the method is that a paper patch is
likely to peel and clog the film gate.

It is apparent that the method of Messrs.
Crabtree and Ives described in the fore-
going will meet with the same objections
as that of Mr. Caminetsky. So far as
can be determined from a description of
the Crabtree-Ives process there is no avoid-
ing the; addition of an extra patch layer
on top of the film. If the idea of the
paper patch is rejected for fear of its peel-
ing and clogging the gate, it seems reason-
able to assume that this latest process must
also be rejected for equally good reasons.

Both suggestions apparently were
prompted by the idea of improving sound
reproduction, yet neither guarantees the ,
safety which is necessary with all film \ \
projection, sound or silent.

December, 1929

The Motion Picture Projectionist

YOU'RE NOT
SUPPOSED TO
BE A FIREMAN

BUT

When fire leaps out in the
booth you are the only one
to fight the red menace—

Your burns may be slight or
again they may be mighty
serious

Whatever clanger occurs you
must face it first and alone—

The wise projectionist boosts

SENTRY SAFETY CONTROL

REMEMBER
YOUR JOB IS TOO IMPORTANT TO WORRY ABOUT FIRE

The Motion Picture Projectionist

December, 1929

Vacuum Tube Theory and Practice

By Edgar iMessing

SOUND pictures placed the projection-
ist in a position where he was called
upon suddenly to apply apparatus
utterly foreign to his previous professional
experience. He was asked to handle equip-
ment about which he knew little or noth-
ing, and it might be said that the facilities
for acquiring in a short time the neces-
sary knowledge to put over a first-class
show were beyond his reach. Withal he
was expected to handle this new equip-
ment well and to project a show equally
as good as the silent-picture standard.
Further, we should remember that the pro-
jectionist must work under the handicap of
knowing that even a small mistake will
immediately manifest itself in poor screen
results.

A good knowledge of this new apparatus
is indispensable to the modern projection-
ist, who realizes fully that he can properly
use only that equipment which he under-
stands. If he has played with radio sets
and displayed a lively interest in the prog-
ress of that art, he has a good start and
the proper frame of mind with which to
■ approach the problems of his sound pic-
ture apparatus.

The heart of sound reproducing ap-
paratus is the vacuum tube. This marvel
of science has made possible modern radio
broadcasting, long distance telephony and
sound pictures. New uses are found for it
every day. It is not difficult to learn how
it works, and to understand why it works
is to know some interesting phases of
electrical theory. It is the purpose of this
series of papers, of which this is the first,
to explain in detail how and why the
vacuum tube performs as it does. Such ex-
planation will necessarily involve the prin-
ciples of amplifying apparatus in which
we are primarily interested. Some of the
material presented ~herein may seem at
first sight to be fundamental and not di-
rectly related to vacuum tubes, but as the
series progresses certain applications will
be described which lead directly back to
the elementary information which will be
offered first.

The ordinary vacuum tube-triode, valve,
audion, as it is variously known — consists
of an evacuated glass bulb containing three
elements — a filament, a grid, and a plate.
The filament is heated by an electric cur-
rent and emits electrons. These electrons
pass to the plate through the grid. The
potential variations on the grid control
the number of electrons passing between
the filament and the plate.

The Electron Theory

The basis of explanation is the electron
theory and we shall go into this at some
length before we come back to a considera-
tion of the vacuum tube. According to this
theory, all matter is fundamentally com-
posed of electric charges, that is, every-
thing that we know existing as liquid,
solid, or gas is basically made up of one
thing. Different kinds of matter differ in

that they contain varying amounts of this
one thing.

Matter may be chemically classified into
various "elements" ; in other words, a
substance may be divided into its con-
stituents and these parts broken up still
further into their components until there
remain substances that cannot be sub-
divided. No one of these final substances
may resemble the original. As a simple
example : — water we know to be composed
of hydrogen and oxygen. Passing an elec-
tric current through water will cause it
to break up into these two parts. Oxygen
and hydrogen normally are gases and in
no way resemble water. No matter what
further operations may be applied to either
of these we cannot subdivide them into

Nuclei w«th

^/ec/roYi

f/ecf-royi

Figure 1 — Representation of an atom with
positive charge.

different substances. Such substances we
call "elements," of which the more com-
mon ones are copper, iron, zinc and lead.
The smallest part of these elements that
are distinct as part of the element . we
call the atom.

Composition of the Atom

It has been established that every atom
of matter is charged with minute particles
of electricity, or electrons. The word
"electron" is used to denote the smallest
unit of electricity. We may for the sake
of convenience picture it as a very small
particle that carries a definite charge of
electricity. We have come to apply the
term to a very small particle of electri-
city that is "negative." Opposed to it
is the "positive" electron, which is of equal
value and which some now call proton.
Both are charges of electricity, and it is
because of certain characteristics peculiar
to each and their marked behavior to
each other and to themselves that we
distinguish one as positive and the other
as negative.

The law that these charges always fol-
low is that like charges repel each other

and unlike charges attract each other. Two
electrons, therefore, will not remain in each
other's company ; while a proton and an
electron will be attracted to each other.
An electron, when separated from the
atom to which it is attached, shows none
of the properties of ordinary matter. It
does not react chemically with other elec-
trons to produce new substances, even
though the elements from which they come
may do so. An electron from the hydrogen
atom is exactly similar to that from an
atom of copper or zinc or tin, or any other
substance.

Within the atom is a positive charge of
electricity in the form of a nucleus, and
close to it, in accordance with the funda-
mental law of unlike charges attracting
each other, is an electron or a number of
electrons, depending upon the atom of the
particular element being considered. As
previously stated, the difference between
the elements lies in the number of charges
in their atoms. Hydrogen, for example,
has but one electron about its nucleus ;
copper has twenty-nine. Some substances
have positive nuclei that will hold even
more electrons.

Under normal conditions the atom has
just enough . electrons or negative bits of
electricity to satisfy the positive nucleus.
However, if something should happen to
the atom and one electron be removed, con-
ditions would no longer be normal — the
atom has a positive charge that is un-
satisfied and the whole atom is therefore
considered positively charged. (Fig. 1.)
Similarly if by one means or another an
extra electron were introduced into the
atom, there would be an unsatisfied nega-
tive charge and the atom would be con-
sidered negative.. (Fig. 2.)

Under either of these conditions the atom
has a new name : it is called an ion, and
the process of adding or subtracting an
electron is called ionization. In the fila-
ment of a vacuum tube we are continually
removing electrons by the application of
heat.

BY conductivity is meant the ability
of a substance to pass an electric
current. What an electric current is we
shall presently see. In conducting solids
there exist atomic systems in which the
number of electrons, free or easily freed
by the application of a potential, such as
a battery, is comparatively large. These
electrons we call free electrons, and while
they may be relatively free from an atom,
they cannot fly off from the substance it-
self, which is the condition that we want to
secure in a vacuum tube. The force that
holds the electron in the substance will
be discussed later. The substance that do
not have free or easily freed electrons are
known as insulators.

A battery has the effect of being a
source of electrons : at one terminal we
may imagine a great many extra electrons

December, 1929

The Motion Picture Projectionist

ftjfc/ec/s With

Extrct
Electron

E/ecfr

roy?s

Figure 2 — Representation of an atom
with negative charge.

and at the other terminal a corresponding
lack of electrons. When we connect the
terminals of a battery to the ends of a
body that has many free electrons, these
are attracted to that terminal of the
battery which lacks electrons ; while at
the other terminal where electrons are
plentiful these stream off into the con-
ducting substance to replace the free elec-
trons. We now have a stream of electrons
moving along the conductor from one
terminal to the other, and we say that
we have an electric current. An electron
in motion constitutes an electric current.
The amount of electricity carried by one
electron is immeasurably small. The num-
ber of electrons required to light a 100-
watt lamp is on the order of ten billion
billion each second, and this corresponds to
a current of one ampere. This stream of
electrons passing through the conductor
will constantly be colliding with free atoms
and creating additional free electrons,
which in turn will stream along to knock
off more electrons from other atoms. The
speed with which the electron stream
travels along a conductor is quite small,
due to the close packing of the atoms and
the resultant little free space in which
the electrons may pick up speed. The vast
number of collisions which ensue have the
effect of slowing up the electrons, so that
while they are whirling around at a high
rate of speed, they may be drifting for-
ward quite slowly.

Direction of Current Flow

It has been accepted as fact by most
people that when the terminals of a battery
are connected to some sort of conducting
path, the direction of current flow is from
the positive pole of the battery to the
negative pole. But from what we have
just reviewed we find that this is not so: —
the electrons flow from that pole which
has an excess of them (the negative),
to the pole that lacks electrons (the posi-
tive) , and that the current flow is from
negative to positive. Therefore, when men-
tion is made of current flowing from posi-
tive to negative, it must be remembered
that what is actually happening is that
electrons are flowing from negative to
positive. In a vacuum tube the electrons
that are thrown off the filament, which
is made negative with respect to the plate,

flow to the positive plate, and the current
flow is from negative to positive.

It must not be construed by the reader
that when we say electrons are passing
along a conductor we mean that actual
bits of material are passing. The atoms .
comprising the substance are practically
fixed in position, although they do' perform
some irregular motions ; but there is no
movement of atoms progressively along
the conductor, as there is a movement of
electrons. We do not have a copper wire
carrying itself from one terminal to an-
other.

Resistance

We have considered the case of a con-
ductor and the non-conductor, or insulator :
— one has a great number of free electrons,
and the other has none. Conductors differ
in the number of free electrons which act
to pss an electric current. The hindrance
which conductors offer to the free progress

of free electrons is called the resistance
of the conductor. This quality differs in
different rnetals. There are more free
electrons in copper than in iron, and we
therefore say that aluminum offers less
resistance to electric current than does
iron.

This value of resistance varies with the
temperature of the conductor. At high
enough temperatures insulators and non-
conductors may act as conductors, while
the resistance of conductors may be ap-
preciably lessened. The reason for this
is that heat gives energy to the electrons
and they move faster and faster in their
paths, so that the hold of the positive
nucleus is weakened and there is possibility
of more electrons being freed. Similarly,
the passage of an electric current stirs up
the electrons and the greater number of
collisions that occur.

(To be Continued)

Progress in Color and Wide Film

THE most important items of progress
within the past six months in the
technical branches of the motion picture
industry have been the extensive use of all-
color sound pictures, or pictures with ex-
tensive color inserts, and several demon-
strations of enlarged projected pictures by
the use of film wider than 35 mm., accord-
ing to the report of the Progress Commit-
tee of the S.M.P.E. submitted at the recent
Fall Meeting of that organization.

Only two-color subtractive processes are
at present in vogue and in one process ex-
tensively employed, two dye images are
produced in a single layer film by imbibi-
tion. Although some three-color imbibition
films have been prepared, they have not
been publicly displayed.

Wide Film Advances

To date only one type of wide film has
been put on the rnarket, this being 70 mm.
wide. Comment of the trade has been most
enthusiastic with regard to its suitability
for scenics and news events, but it is ap-
parent that a new photographic technie is
required to secure more pleasing perspec-
tive in the case of photoplays. Difficulties
involved in the more universal adoption of
the wide film are the present lack of stand-
ardization of size, the necessity for greater
illumination at the projector aperture, and
the prevention of film buckle.

Silent Films Total 5%

Studios in Hollywood are now produc-
ing only about 5 per cent of silent pictures.
When it is considered that only one year
ago the first dramatic pictures were shown
before the Society, notably "The Singing
Fool," the remarkable progress made since
that time is apparent. There has been a
steady improvement in the quality of sound
reproduction, notably in the theatre, but in
many cases the quality in the theatre falls
far short of that which the film is capable
of producing when it leaves the studio.
Much still remains to be done in the way
of improvement even with the best of re-
cording. With the high quality music
given by the modern radio receivers the
public is realizing that the average theatre

music is not equal in quality to that ema-
nating from their radios at home.

Notable advances in studio technie have
been (a) the tendency to use a minimum
number of microphones and eliminate
"mixing," (b) the silencing of cameras such
as by means of insulating coverings thus
permitting greater freedom of camera lo-
cation, ( c ) the tendency to use more live
studios so as to simulate more closely
natural sounds, and (d) the non-simultane-
ous recording of scene and sound.

Improved Reproducers

A noteworthy advance in reproducers has
been the introduction of the condensor or
electrostatic reproducer consisting of a rub-
ber diaphragm coated with aluminum foil
and stretched across a metal grid. Apart
from the high quality resulting, the repro-
ducer occupies no more space than the
average screen and can be raised and low-
ered just as easily.

No fundamental advances have been
made in the field of stereoscopic motion
pictures and although some of the spon-
sors claim that their wide film processes
give stereoscopic effects, they are at the
most pseudo-stereoscopic. A much higher
order of relief is noticeable in many of the
pictures in color.

Television Remote

Although color pictures have been tele-
vised during the past six months, the prob-
ability of television usurping the present
motion picture in the immediate future ap-
pears to be very remote.

Pacent Service Stations

Besides its regular service facilities
from Coast to Coast, through established
representatives, seven new service depots
of Pacent Reproducer Corporation, which
will operate under the direct control of
the New York office, are now functioning
in New Orleans, Atlanta, Memphis, Okla-
homa City, Albany, Denver and Des
Moines. In each of these cities Pacent
service men, controlled by headquarters in
New York, are rendering inspection and
maintenance service to exhibitors as well
as emergency service when needed.

The Motion Picture Projectionist

December, 1929

P. A. C. Luncheon to President Canavan

WITH practically every branch of
the motion picture industry repre-
sented by one or more delegates,
the Projection Advisory Council luncheon
tendered President William F. Canavan of
the I. A. T. S. E. & M. P. M. O. U. at
the Hotel Astor, New York City, on
November 14th was by far the most suc-
cessful and significant gathering in the in-
terest of projection and projectionists that
has ever been held. As a matter of fact,
it was the first gathering on record
strictly in the interest of projection at which
all branches of the industry were repre-
sented. More than 175 people were present,
and among this number were studio tech-
nicians, stagehands, executives, managers,
projectionists, cinematographers, manufac-
turers, newspapermen and labor leaders —
all gathered together for one purpose and
that to better projection.

Local Unions of the I. A. themselves set
the pace for the meeting, with delegates
from more than 20 Locals in nine different
states being present. Delegations from
Boston, Newark, Rochester, New York
City, Schenectady, Providence, New Haven,
Jersey City, Atlantic City, Philadelphia,
Washington, D. C. ; ■ Scranton, Easton, and
many other cities were present. Identities
were ignored in the seating arrangements,
thus an entente cordiale was established at
once that went far to insure the success of
the affair.

President Canavan's Address

Assembling for luncheon at 12 :30 P. M.
sharp, the meeting continued until well after
4 o'clock, during which period there wasn't
a dull moment. It can be said that the
luncheon was excellent, but this might
publicly be said to be a minor detail (that
is, publicly). After cigars and demi tasse,
the gathering settled down to the business
at hand, of which there seemed to be so
much that only a fraction of the potential

William F. Canavan

discussion surging in the breasts of those
present could be invited.

The highlight of the afternoon was
President Canavan's address, a complete
transcript of which is appended hereto.
After reading a prepared address in which
he cited the growth of the motion picture
industry with its attendant increasing re-
sponsibilities for the projectionists, Presi-
dent Canavan launched into an extem-
poraneous talk in which he stressed the
desire and the ability of the projectionist
to do quality work, the injustice of the
many critical comments made regarding
projection work, and the necessity under
existing conditions for the projectionist to
devote more and more of his leisure time
to the study of and practice with his
equipment in order that he might turn in
the best possible performance.

President Canavan emphasized the fact
that, within his experience with the Ameri-
can labor movement, he knew of "no group
of wage-earners which has given as much
time to the scientific consideration of their
work as motion picture projectionists."

Following President Canavan's address,
toastmaster Lester B. Isaac, Supervisor of
Projection for Loew Theatres, Inc., and
President of the P. A. C, introduced Sam
Kaplan, President of Local 306. Mr. Kap-
lan cited the progress made by the craft
in the last two years and complimented
the officers of the Council for their fine
work. He added that the Council might
expect the active cooperation of the entire
membership of Local Union 306 in all its
endeavors and stated that he felt sure he
might speak similarly for every other Local
Union in the Alliance. The manner in
which the projectionist mastered the intri-
cacies of sound picture reproduction, said
Mr. Kaplan, was the best index as to the
worth of the craft and of its ability to
produce quality work consistently.

The Local 306 leader disclosed the fact
that when he entered the luncheon room
he was amazed at the number of repre-
sentative guests who were in attendance,
adding that had anyone suggested the pos-
sibility of such a meeting purely in the
interest of projection prior to the very day
it happened, he would have been unable to
believe it possible. He closed his remarks
by suggesting that now that the "ball had
started rolling in the right direction, let
us keep it going."

Following the introduction by Mr. Isaac
of a number of well-known guests present,
Charles F. Eichhorn, Vice-President of
Local Union 306, opened the forum for dis-
cussion. Among the topics which came up
for discussion during the forum was the
effect of faulty recording on sound repro-
duction; the radio campaign of Boston
(Continued on page 34)

General view of dining room at P. A. C. luncheon to Pres. Canavan of I. A.

ecember,

1929

The Motion Picture Projectionist

Elementary Optics

WHEN light is transmitted from
one medium to another several
things can happen to it : the
light may be reflected from the second
medium; it may be dispersed (reflected in
many different directions) ; refracted, or
polarized. The study of just what hap-
pens under these various conditions is
known as the science of optics. In order
to visualize just what does happen under
these conditions, it is convenient to con-
sider the light traveling from the source
in one direction only. This beam of light
is generally represented by an arrow.

The diagram in Fig. 1 shows a beam of
light from a source passing through a
piece of glass and striking a piece of white
paper. The light, when hitting the glass,
is partly reflected and partly transmitted
through the surface of the glass. The

Types of Lenses

light that is transmitted through the glass
is bent out of its original path. This is
termed "refraction."

Reflection

By far the simplest of all light effects
is reflection. The law for reflection in-
volves no experimental constants, but
merely states and means that the angle of
reflection is equal to the angle of inci-
dence. This is illustrated in Figure 2.
When this surface is flat we get an ordi-
nary mirror; but when the surface is
curved, we get many peculiar effects. It
is possible to make an optical system for
a camera, a projector, a telescope, and
many other things, with a set of reflectors.

Supposing we take a part of a hollow
silvered ball (Fig. 3), and place an ob-
ject in front of the curved portion. In
this figure we will consider the object as
an arrow. If we take two points off this
arrow, and take two rays of light from
each point and trace them to the mirror
and back, we will find that all the rays
striking the mirror from any point in the
object will intersect at some one point
after leaving the mirror. If a white piece
of paper be placed at this intersection, the

By Samuel Bagno

Figure 3

image, or picture of the object, will be
seen on that paper.

Another important application of a
curved mirror is that of a mirror so de-
signed as to reflect all the rays of light
from point source parallel to each other.
The slope at every point must be such as
to accomplish this purpose. Such a mir-
ror is placed in back of the arc on a mo-
tion picture projector, and also in a beam
searchlight. If it were possible to build
a perfect parabolic reflector, a beam of

Figure I

Figure 2

light could go on almost endlessly with-
out losing much of its original intensity.
Such a reflector is pictured in Fig. 4.

Fundamentals

Before we consider the laws of refrac-
tion it would be better to review a few
fundamental definitions. These are :

1. An angle is the entire portion of
space between two intersecting lines.

2. The entire space around any point
is divided into 360°.

3. A right angle is one-quarter of the
space around any point, thus: (% of 360",
or 90°).

4. A perpendicular to a line is a line
at right angles to it.

5. A circular arc is a portion of a
circle. This is measured in degrees and
is equal numerically to the angle inter-
cepted by two lines from the center of a
circle to the extremities of a circular arc.

6. The sine of an angle is perpendicu-
lar dropped from one end of the arc on
to the more radius at the other end of the
arc, divided by the length of the radius.
This is shown in Fig. 5.

7. The angle of incidence of a ray of
light is the angle formed by the incident

ray and the normal (or perpendicular), to
the surface at the point at which the ray
strikes it. This is pictured in Fig. 6.

8. The angle of refraction likewise is
the angle formed by the refracted light
and the perpendicular to the surface
through which the ray of light emanates.
Also shown in Fig. 6.

It was not until the latter part of the
eighteenth century that a general law ex-
plaining all refraction was formulated.
Before this time the manufacture of all
lens systems was merely a matter of ex-
periment. As far back as the thirteenth
century Bacon predicted the application of
the lens systems we have today — the tele-
scopes, microscopes, and even the magic
lanterns. However, not' until the law of

\a ■ V

Figure 4

refraction was formulated some 500 years
later were these instruments made prac-
ticable.

Law of Refraction

This law, while extremely important, is
one of the simplest : It states that the
sine of the angle of incidence divided by
the sine of the angle of refraction, is a
constant. This constant can be deter-
mined for a flat glass plate by observing
how a ray of light, striking slantingly
against the surface of the glass, is bent in
passing through it. Once this constant
is determined, the design of any lens sys-
tem to accomplish any desired purpose
can be determined. Lenses are generally
built with spherical faces in order to fa-
cilitate the grinding process. Fortunately
this type of lens lends itself to almost any
desired purpose.

The principle of tracing several rays of
light is used in calculating every type of
lens system. The simplest and perhaps
the most useful optical system is the cam-

°r /?sf,

ricf/c,^

Figure 6

The Motion Picture Projectionist

ecember,

1929

Figure 7
era. The principle of this instrument is
shown in Fig. 7.

The camera is the essence of the pro-
jector and of the optical system for the
sound track. By means of it the image
of the film is concentrated on the screen,
or the image of a mechanical slit is con-
centrated on the film.

Of particular interest is the fact that

rays of light of different colors are bent
differently when passing through the same
piece of glass. A violet ray is bent the
most, and the other colors of the spec-
trum are bent according to the way they
follow violet in the spectrum : — blue, green,
yellow, orange, and red. This is known as
chromatic aberration.

However, since different kinds of glass
possess this property in different degrees,
this condition may be compensated for by
putting a hollow and a bulging lens to-
gether. The image resulting from this
combination is not distorted by the color
effects of the light.

Standard Nomenclature

(The following glossary of technical terms
used in the motion picture industry was
formulated by an S.M.P.E. committee
and adopted as standard by that organi-
sation. Trans. Vol. XIII, No. 37.)

ACTINIC— Having the property,
possessed especially by the shorter
wave lengths of the spectrum, of effect-
ing chemical changes as in photography.

Acoustic Flat — Set Flat treated to
secure sound absorption.

Additive Process — Color processes in
which various hues are obtained by the
addition of two or more of the spectral
regions comprising white light.

Alternating Current — Current which
flows first in one direction and then the
reverse, due to the regularly recurring
alternation of potential of the generator.

Ampere — The unit of measure of elec-
trical current.

Amplification — The ratio of the volt-
age or current output to voltage or cur-
rent input respectively.

Amplification Factor — The amplifica-
tion factor of a three-electrode vacuum
tube is the ratio of the change in static
plate potential to an infinitesimal change
in that static grid potential, all other
variables remaining constant.

Amplitude — In any vibratory motion,
the extent of movement from the mean
position to the extreme.

Angle of Incidence — The angle which
an incident ray of light forms with the
normal to the surface.

Angle of Reflection — The angle which
a reflected ray of light forms with the
normal to a surface.

Aperture — The opening in the aperture
plate at which each individual picture is
situated during exposure, printing or
projection, respectively.

Aperture Plate — In a motion picture
projector, printer, or camera, a plate of
metal containing the actual aperture
opening.

Arc — A column of very hot light-
emitting gas, carrying an electric cur-
rent sustaining this condition.

Attenuation — The inverse of gain
measured in the same units as gain.

Back-Focus — The distance from the
principal focus of a lens to its nearest
face.

Baffle Blanket — Felt sheets covered on
both sides with muslin and distributed
about the set to make it acoustically sat-
isfactory for sound recording.

Beat — Interference between two wave
trains resulting in alternate reinforce-
ment and destruction of the one by the
other.

Bel — Ten decibels.

Blooping Patch— A triangular black
section introduced over a splice on the
positive sound track, to prevent the noise
which the splice would otherwise cause
during reproduction. The patch effects
a relatively gradual diminuation in the
transmitted light, followed by gradual
restoration to the original value. The
frequency of the diaphragm movement
thus caused being below the threshold
of audibility, no sound is heard. The
patch may be applied by stencilling writh
black lacquer, or may be a triangle of
black paper or film cemented on the
track.

Brightness of a Surface — The lumi-
nous intensity per unit of projected area.

Bullet-type Microphone — A condenser
microphone and microphone amplifier
mounted in a small case.

Business — Action by the player; e.g.,
business of shutting door.

Camera Booth — Sound-proof inclosure
for cameras employed to prevent camera
noises from interfering with recorded
sounds.

Camera Marker — The device for mark-
ing the picture negative.

Camera Motor — A motor for driving
a motion picture camera.

Candlepower — The luminous intensity
expressed in candles.

Change-Over — In projection, the act
of changing from one projector to
another preferable without interrupting
the continuity of projection.

Cine — A prefix used in description of
the motion picture art or apparatus.

Close-up — Scene or action taken with
the character close to the camera.

Condenser — The lens combination
which refracts the diverging rays of the
luminant into the projection lens.

Collecting Lens — The lens of the con-
denser nearest the light source.

Converging Lens — The lens nearest
the objective.

Center Lens — The lens of a three lens
combination lying between the collecting
lens and the converging lens.

Contrast — The ratio of the highest to
the lowest value of transmission. The
range of tones in a negative or print.

Cooling Plate — A shield or baffle, com-
posed of one or more plates, mounted
between the light source and the
mechanism, and usually attached to the
latter but spaced therefrom, to prevent
overheating the mechanism.

Cut-back — Scenes which are returns
to previous action.

Cut-in — Anything inserted in a scene
which breaks its continuity.

Cutting— Editing a picture by eliminat-
ing unsuitable subject matter therefrom,

Developing — Chemically treating ex-
posed film to make the latent image
visible.

Diffuse Density — The value of density
in which the total transmitted intensity
is measured. (This value of density is
applicable to contact printing relations.)

Direct Current — An uniform flow of
electric current in one direction as from
a battery or direct current generator.

Director — The person who superin-
tends the actual production of the
motion picture.

Dissolve — The gradual transition of
one scene into another.

Distortion (of Sound) — Modification
of sound caused by the means employed
in its recording and reproduction.

Double Exposure — The exposure of a
negative film in a camera twice before
development.

Douser — The fire-proof shutter usually
mounted on the lamp house of a motion
picture projector or stereopticon by
means of which the light may be inter-
cepted before it reaches the film or
slide.

Dubbing — The re-recording by elec-
trical means of a sound record or portion
thereof. The operation may involve
transference from film to wax, wax to
wax, or wax to film. Dubbing is re-
sorted to for editorial purposes, for
changing volume levels, and for chang-
ing the recording medium.

Effective Aperture — The largest diam-
eter of a lens available under the con-
ditions considered.

Electrical Filter — A network of elec-
tric circuit elements designed to pass or
suppress one or more bands of fre-
quencies.

Equivalent Focal Length — The equiv-
alent focal length of a combination of
lenses is equal to the focal length of a
simple thin lens which will give an image
of a distance object of the same, size as
does the combination lens.

Exciter Lamp — The light source used
in reproducing sound from a film.

Exposure — (1) The product of time
and the illumination incident upon the

(Continued on page 40)

December, 1929

The Motion Picture Projectionist

Disc Pick-up Intricate Process

Victor L. Osgood

(Copyright, 1929, by Victor L. Osgood)

THE method of recording music on
a wax cylinder or disc, to be later
reproduced, is quite common knowl-
edge because of the simplicity of the ap-
paratus involved and also -because the
phonograph has been in use for a full
generation. But the process of reproduc-
ing that recorded music through a speaker
is not only a more complicated matter, but
is a much newer invention, considerably
less understood, due to its electrical na-
ture and lack of explanation.

It may be added here that the orthodox
type of pick-up (as these units are called),
is today still considerably removed from
the perfected state. This applies especially
to permanence and efficiency, though we
are not primarily concerned with the latter,
for what radio apparatus is efficient? If
we get enough energy from the pick-up to
compare favorably with that delivered by
the radio frequency amplifier, on a loud
signal, to the audio system, we are going
to have plenty of signal strength from the
loud speaker.

Tubes Easily Overloaded

An average potential of one volt gen-
erated by the pick-up will produce over-
loading on a single tube, and is the limit
that the first stage audio tube will stand
without overloading unless it is equipped
with a high plate and grid voltage.

Quality of reproduction is a more vital
factor than efficiency. To have all fre-
quencies generate the same value of volt-
age is the ideal condition, when used with
an amplifier and speaker that do not have
frequency characteristics. But amplifiers
and speakers do have frequency character-
tics and consequently the ideal pick-up is
one that makes up for the discrepancies of
the succeeding apparatus.

However, the ideal condition is seldom
attained, and if it be approached in prac-
tice, the remaining deficiencies are over-
locked by the human ear. Therefore, a
pick-up, to be considered very good, must
be sensitive enough to supply about J4 of
a volt in the region of a thousand cycles,
to have no sharp resonamce peaks, and
have a fairly high and low cutoff, say
4,000 cycles and 60 cycles, respectively.
It will also be better if it has a rising
characteristic below 250 cycles, because
record manufacturers do not cut these fre-
quencies with their proper relative ampli-
tude, due to lack of space between grooves.
The fact that amplifiers have a drop in
amplification at those low frequencies adds

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to the desirability of the rising character-
istic.

The curve should taper off, too, at about
2,500 cycles, because the needle scratch
region is entered at that point and the
scratch is very objectionable if not fil-
tered. And the filtering merely tapers off
the high end, which characteristic might
just as well be incorporated in the pick-up
design.

Stopping Needle Scratch

Another very important point in the de-
sign of a pick-up is the mechanical imped-
ance of the needle point. Too stiff a nee-
dlt will result in excessive side wear on
the record grooves and will even break
them through at times. This, of course,
results in impaired reproduction and, later
on, a ruined record.

Permanence, mentioned before, is much
more important than we might at first
suppose. In this respect, aside from wear
and improper handling, there are two
main vulnerable points : ( 1 ) the strength
of the magnet, and (2) thej life of the
rubber bearings and dampers. If a pick-
up when purchased, is considered as being
a permanent installation without troubles,
a certain amount of disappointment must
follow if the magnetic structure is not
properly designed or if the armature is
mounted on rubber bearings and adjusted
with rubber dampers.

Strur ure of Air Gap

The magnetic structure is mentioned be-
cause the writer has had occasion to ex-
amine a large number of different makes
during the last year and has found that the
majority do not come up to certain specifi-
cations determined emphatically by the
Bureau of Standards for maintaining life.
There is a gradual decrease of field
strength in the magnet, with a correspond-
ing decrease of response in the tiny gen-
erator it excites, this decrease being quite
heavy at first and diminishing gradually.

That is, the less the strength of the mag-
net, the less the demagnetizing force.

The Bureau of Standards states that, in
order that cobalt steel retain its magnetic
field indefinitely, the equivalent air gap
(summed up from the several gaps) must
be so proportioned that :

Length of magnet (cross section of
mag.) x cross section of gap (length of
gap) is equal to or greater than 35, as-
suming that the iron structure has suffi-
cient cross section to carry the field with-
out saturating. In the case of tungsten
steel, this product must equal or be greater
than seventy. This fact largely accounts
for cobalt being used so widely, because
it is difficult, in the usual type of pick-up
mechanism, to have an equivalent gap that
will satisfy the tungsten equation without
introducing some other objectionable fea-
tures.

Needle Upsets Balance

Figure 1 shows both the theory and
practice that has been used in the past
for the better grades of pick-ups, the only
difference in the various makes being in
the proportioning of parts and gaps.

This structure is a "bridge" circuit, an
exact duplicate, magnetically, of the elec-
trical Wheatstone bridge. The needle mo- "
tion upsets the balanced condition of the
bridge, in degrees and at frequencies cor-
responding to the amplitude and frequency,
respectively, of the recorded sound.

Since, in a static condition, the magnetic
field is absent in the armature, all the flux
flows across the gaps at each end of the
armature without any of it threading the
coil. But a movement to either side of
the static position will result in some flux
in the armature, its polarity being deter-
mined by the direction of armature dis-
placement and its amount by the amplitude
of motion.

The fact that alternating flux is pro-
duced in the armature by a mechanical
movement back and forth each side of the
balanced position may be better understood
by an examination of Figure 2, which is
a schematic diagram of an equivalent elec-
trical circuit. Here the battery corresponds
to the magnet, the resistors to the air gaps
and the movable contact arm to the arma-
ture. Anyone only slightly familiar with
electricity will readily see why current
flows in the direction shown by the arrows
in the respective positions of the contact
arm.

The coil is wound over the armature on
a spool which does not make mechanical
contact with any of the moving parts, as
this would introduce distortion from fric-
tion, or, if the pressure were very heavy,
the mechanical impedance of the needle
goes up excessively, eliminating high and
low frequencies and causing extreme wear
on the record grooves.

Since rubber is an impermanent mate-
rial, the gaps cannot be adjusted so that
the motion of the armature includes more
than a small percentage of them. It js
obvious, in Figure 2, that the more the
(Continued on page 32)

The Motion Picture Projectionist

December, 1929

As The Editor Sees It

S^ Improved Reproduction Facilities
OUND pictures have improved tremendously since
their introduction on a commercial basis, but the quality
of many sound pictures as presented in not a few theatres
today is anything but what it should be. Improvements
have been noted in recording and reproduction technique,
but little advance can be credited to the accessories for
good recording and reproduction. The projector still
is loaded down with many extra "gadgets" which in many
cases serve only to harass the projectionist in his efforts
to put on a good show. We often come across a com-
mentary on the ideal type of speaker, but can anyone prove
that the present sound picture horn is but a step advanced
over the early speakers in its reproducing quality?

Then there is the old, old complaint on the score of good
screen results. Screen manufacturers are bending every
effort to solve this highly important problem of screen
light values, but they still have a long way to travel before
their task is ended — our opinion being that the present
positioning of the horns will prove a stumbling block in
this respect for quite some time to come. Screen results
in many theatres today are very poor when one recalls the
progress that was being made in this respect before the
coming of sound. Sound with pictures is all very well,
but we must have a picture which is bearable to look at.

We all are one in lauding the progress that is being
made in the development of the sound picture art, but we
often wonder if it wouldn't be just a bit better to detach
a force to act as a rear guard the while this grand and
glorious army of electrical entertainment technicians
pushes onward to win new battles in the realm of the
scientific unknown.

E^P.A.C. Luncheon in New York
ASILY the outstanding development in projection
circles within the past month, and for many months past,
was the luncheon tendered President William F. Canavan
of the I. A. T. S. E. by the Projection Advisory Council
on November 14th at the Hotel Astor in New York City.
The affair was a grand success in itself, but the importance
of the gathering from a projection viewpoint may not be
judged fairly by any social yardstick. To anyone who has
followed closely the battles of the past for recognition of
the importance of projection and the projectionist in the
scheme of things in the motion picture theatre, this affair
was a revelation — a revelation of the new prestige which
has been won by the craft for its splendid work of the past
two years. Anyone who had proposed such an event one
year ago would have been laughed at ; yet in a mere twelve
months such a gathering passed beyond the stage of pos-
sibility and became an actuality.

Gathered together in one room were more than 175
friends of better projection — executives, managers,
engineers, newspapermen, cinematographers, stagehands,
manufacturers, labor leaders, and projectionists. The
luncheon was arranged ostensibly for the purpose of pro-
viding the press with an opportunity for becoming better
acquainted with the problems of projection, with President
Canavan cheerfully accepting the invitation to act as the
principal liaison officer. While the press conference was
necessarily curtailed, it may tie said that the luncheon, even
without a press conference, accomplished far more than its
sponsors hoped for. A few problems were discussed,
indeed, but it is certain that the affair did more to promote
a better understanding between the various branches of

the industry represented in the room than would a whole
afternoon session devoted to a discussion of problems.

Incidentally, one of our pet contentions was sustained
by the affair, for there before our startled gaze were the
accredited delegates of nearly a score of Local Unions,
officially designated by their fellow members to represent
them at the meeting. This interest on the part of the Local
Unions in the quality as well as the quantity of work done
by their members was extremely cheering. And we feel
certain that not a single delegate to the meeting can honest-
ly say that his trip to New York was not time well-spent.

There were many other highlights of the gathering, too
numerous to mention here. Elsewhere in this issue there
appears a detailed account of the luncheon, with a complete
list of those attending. The list of guests is impressive,
judged from any standpoint. The affair was provocative
■of much good fellowship and not a little interchange of
valuable information. It reflects much credit on its spon-
sors, particularly on P. A. McGuire of the International
Projector Corp., who worked long and hard to insure the
success of the affair. Mr. McGuire was ably assisted by
many co-workers, chief of whom was Charles F. Eichhorn,
Vice-President of Local Union 306.

ACJ More on Wide Film
SHORT while ago there was offered in a Broadway
theatre the first public presentation of a new motion picture
film size, which we term "wide film," the while disdaining
the fanciful names which have been appended to the few
systems which have already been shown or will be shown
within the next few months. Following this first public
showing, the uproar which was occasioned by it seems to
have died away to a whisper. But let us not check this
venture off as "just another one of those things," the latest
failure in a series of technical developments which are
accredited as being absolutely "the last word." For we
have not heard the last word on this important matter, not
by far.

The various companies interested in a wide film process
are merely marking time, devoting their time to improv-
ing this and that feature of their equipment and
strengthening their lines in general. The most encourag-
ing aspect of this new development is, as we stated previ-
ously, the fact that there is much work and little talk, the
latter being the usual accompaniment to all too many
"last word" disclosures in the scientific field. It is under-
stood that Fox plans to introduce its Grandeur system to
the general exhibition field via an installation in the Roxy
Theatre ( N. Y ) , not later than next February. RCA has
formally announced its acquisition of the Spoor-Berggren
process rights and is planning an intensive campaign all
along the line. Little or nothing has been heard from
Paramount on its Magnafilm, but it is safe to assume that
they are working feverishly to perfect the system.

When wide film does begin to catch on it will probably
follow the same path as did sound pictures— it will arrive
with little fanfare, take hold suddenly and be here before
we quite know just how it all happened. Information
on the different processes, which we have promised for
these columns, is impossible to get, so closely are the vari-
ous owners guarding their secrets. As we stated before,
projectionists need have no great concern about their
responsibilities with this new equipment. Increased care
and watchfulness is about all this new development will
demand of the projectionist.

December, 1929

The Motion Picture Projectionist

Everyday Science

Carbon Dioxide

A PRODUCT of burning. When any
fuel, such as coal, gas, oil, or wood,
burns, it sends forth gases into the sur-
rounding atmosphere. These gases, like
air, are invisible, and were unknown to us
for a long time. The chief gas formed by
burning substance is called carbon dioxide
(COi) because it is composed of one part
carbon and two parts of oxygen. This gas
has the distinction of being the most widely
distributed gaseous compound of the entire
world; it is found in the ocean depth and
on the mountain heights, in brilliantly
lighted rooms, and most abundantly in
manufacturing towns where factory chim-
neys constantly pour forth hot gases and
smoke.

Wood and coal, and in fact all animal
and vegetable matter, contain carbon and
when these substances burn or decay the
carbon in them unites with oxygen and
forms carbon dioxide.

The food which we eat is either animal
or vegetable, and it is made ready for
bodily use by a slow process of burning
within the body; carbon dioxide accompan-
ies this bodily burning of food just as it
accompanies the fires with which we are
more familiar. The carbon dioxide thus
produced within the body escapes into the
atmosphere with the breath.

We see that the source of carbon dioxide
is practically inexhaustible, coming as it
does from every stove, furnace, and car
and further with every breath of a living
organism.

Danger to Health

When carbon dioxide occurs in large
quantities, it is dangerous to health, be-
cause it interferes with normal breathing,
lessening the escape of the waste matter
through the breath and preventing the
access to the lungs of the oxygen necessary
for life. Carbon dioxide is not poisonous,
but it cuts off the supply of oxygen, just
as water cuts it off from a drowning man.

Since every man, woman and child con-
stantly breaths forth carbon dioxide, the
danger is overcrowded rooms is1 great, and
proper ventilation is of vital importance.

Motors' Hum Lights Landing Field

No longer will it be necessary to keep
airplane landing fields brilliantly lighted
all night when a new invention, only re-
cently demonstrated, is perfected to the
point of being manufactured in quantity.
The noise made by the hum of an air-
plane 1,000 feet in the air closed the switch
that lighted a bank of flood lights at a
Pennsylvania aviation field in the first de-
monstration of the sound sensitive auto-
matic lighting apparatus developed by an
electrical research engineer.

The device uses the drone of the air-
plane to control electric energy. From a
tiny current at first this controlled energy
is increased in power by amplifiers until it
is strong enough to throw a good sized
lighting switch.

A loud-speaker operated reversely is the
"ear" of the mechanism. Laid on its back
it gives the apparatus a directive effect
with reference to noises from above. A
microphone completes the auditory section.
Passing through several amplifiers the
impulse then passes through the time-light
relay, the last step before the current auto-
matically throws the lighting switch.

The switch locks automatically and the
lights remain on until the switch is thrown
by a field attendant.

Instability of the Air

We are usually not conscious of the air
around us, but sometimes we realize that
the air is heavy, while at other times we
feel the bracing effect of the atmosphere.
We live in an ocean of air as truly as fish
inhabit an ocean of water. If you have
ever been at the seashore you know that
the ocean is never still for a second;
sometimes the waves surge back and forth
in angry fury, at other times the waves
glide gently in to the shore and the surface
is as smooth as glass ; but we know that
there is perpetual motion of the water even
when the ocean is in its gentlest moods.

Generally our atmosphere is quiet, and
we are utterly unconscious of it ; at other
times wei are painfully aware of it, be-
cause of its furious winds. Then again
we are oppressed by it because of the vast
quantity of vapor which it holds in the
form of fog, or mist. The atmosphere
around us is as restless and varying as is
the water of the sea.

The air at the top of a high tower is
very different from the air at the base of
the tower. Not only does the atmosphere
vary greatly at different altitdues, but it
varies at the same place from time to time,
at one period being heavy and raw, at
another being fresh and invigorating.

Winds, temperature, and humidity all
have a share in determining atmospheric
conditions, and no one of these plays a
small part.

Long-Lived Lamps Too Expensive
to Consumer

AN electric lamp that will give light
for years is too expensive for a cus-
tomer to buy. Occasionally a lamp built
for a thousand hours' service will burn
for years, as was the case recently dis-
covered in New York where a dealer re-
ported that a tungsten lamp had given
service for more than nine years.

As a matter of fact, manufacturers could
make electric lamps to burn nine years or
much longer, but the cost of operating
such lamps would be excessive. Lamps
are designed to give approximately one
thousand hours of continuous light with a
minimum consumption of electricity for
any given amount of light. To make a
lamp last longer it is necessary to put
more material into the filament and it then
requires more current to heat it to the
required temperature.

$10 Additional Cost

For example : A customer might save
5 cents per lamp by buying a carbon fila-
ment instead of a modern tungsten filament
lamp, but the cost of operating it would
be much more. At 10 cents a kilowatt
hour it costs a customer $5 to burn a 50-
watt tungsten lamp one thousand hours,
and it would cost approximately $15 to
burn a carbon filament lamp giving the
same amount of illumination. In other
words, to save 5 cents, the customer would
be obliged to spend $10 more to get the
same amount of illumination.

Moving Strips of Fabric Weighed
Electrically to Test Uniformity

A recent development in automatic elec-
tric weighing has made it possible to weigh
a continuous web of paper, or other ma-
terial, as it passes through the mechanism,
which does not touch the material weighed.
Tuned Radio Circuit

The principles underlying this process
are those of the tuned radio circuit. The
web of material passes between two parallel
metal plates which act as a condenser in
the receiving circuit. Variations in the
weight of the web change the capacity of
the condenser and affect the response of
the circuit to a wave of controlled fre-
quency. These variations are indicated on
a meter, and may also be used to operate
machine controls by suitable relays.

The new weighing process is said to be
of notable value in maintaining uniformity
in the weight of paper.

Cause of Mouth Breathing

Some people find it difficult to breathe
through the nostrils on account of growths,
called adenoids, in the nose. If you have a
tendency toward mouth breathing, let a
physician examine your nose and throat.

Adenoids not only obstruct breathing and
weaken the whole system through lack of
adequate air, but they also press upon the
blood vessels and nerves of the head and
interfere with normal brain development.
Moreover, they interfere in many cases
with the hearing, and in general hinder
activity and growth.

Affects Early Development

The removal of adenoids is simple, and
carries with it only temporary pain and no
danger. Some physicians claim that the
growths disappear in later years, but even
if that is true, the physical and mental
development of earlier years is lost, and
the person is backward in the struggle for
life and achievement.

Gas Now Used as a Refrigerant

Gas — long used for lighting only, but
which can now be used wherever heat is
necessary in the home or industry — has en-
tered the new field of refrigeration. Gas-
fired refrigerators are now on the market
which utilize gas fuel for expanding the
refrigerant, which is ammonia or some
other gas of like properties.

The principal points claimed for gas-fired
refrigeration are absence of moving parts,
quietness, of operation and low cost of
service.

The Motion Picture Projectionist

December, 1 929

Efficient Sound Projection

By R. H. McCullough

Supervisor of Projection, Fox West Coast Theatres

PERSONALLY I have watched hun-
dreds of projectionists putting on a
show. Some were good, some aver-
age, and a few poor. One can usually tell
if the show is going to be a "flop" with
sound and projection and general running
routine. A performance can be rehearsed
too much, the same as a prize fighter can
do too much, training. He is overconfident
and becomes careless, because of mechani-
cal routine. I have seen many projection-
ists work sixty hours without sleep, in-
stalling equipment in a new theatre, and
yet on opening night run the show to the
entire satisfaction of everyone concerned.
But now it is entirely different. Sound
pictures require greater attention.

Projectionists and managers have been
in the habit of waiting until the last minute
before rehearsing premiers, and have
worked a few nights and days up to the
opening hour of the show. This must be
discontinued. Projectionists must step into
the projection room on opening nights well
rested and in good shape — otherwise the
performance may be a complete "flop."

All sound projector systems are provided
with a means for controlling the volume
of the sound — a fader. The face of the
fader box is divided, one side being red
with fifteen numbers, and the other side
white with fifteen numbers, each number
corresponding to one resistance coil, so
that when the pointer is retarded or ad-
vanced one number it has cut-out or cut-
in one of the resistance coils. It is im-
perative that the fader contacts be kept
perfectly clean at all times.

Let us analyze this unit of equipment as
shown in the accompanying illustration.
Switch No. 1 is for the purpose of cutting-
out the fader in case of trouble. Switch

No. 2 is used when three sound projectors
are equipped with sound. No. 3 fader con-
tacts are connected to 30 short coils of
resistance wire in a circle around a metal
disc (No. 4). Arm No. 5 receives current
from disc No. 4 through contact No. 7
to the resistance coil contact, with resist-
ance in series with the pick-up circuit.
No. 6 represents the locating arm, positions
and indentations. The locating arm carries
no current, but acts only as a semi-lock
to hold the fader arm in position. No. 9
is a cast iron frame which has a bearing
for the fader knob shaft and other work-
ing parts. No. 8 identifies rod clamps,
whereby auxiliary dummy faders may be
connected.

The terminal input blocks will be found
at the lower part of the fader. The pro-
jector pick-up circuits are connected to the
input of the fader. The switching panel
to change from disc to film is located
either above the master fader or above the
film pick-up amplifier on the universal base.

Note the output terminal block. The
output leads are connected to the first stage
of amplification. The factor is always lo-
cated between the projector pick-up
circuit and the first stage of amplification.

Rear view of the W. E. 49-A amplifier,

showing input and ouiput transformers;

also grid-biasing resistors.

In case of trouble with the fader, cut-out
the fader by using switch No. 1. The vol-
ume may be either increased or decreased
by the potentiometer on the main amplifier.

Western Electric 49-A Amplifier

The 49-A amplifier is designed to bring
the level of the electrical counterpart o.'
the film sound record up substantially to
the same energy value as that obtained
from the magnetic coils of the disc re-
producer. Note the accompanying sche-
matic diagram of the 49-A amplifier.

The current for the tube filaments is
supplied from a 12-volt source, and is
measured by a series milliammeter. The

t«T£V>

Analytical photo
of W. E. fader,
showing the loca-
tion of various
switches, and in-
terior contacts,
which are de-
scribed in the ac-
companying text.

tfTjjfV?

utput

value of this current is adjusted to 270
milliamperes by a 20-ohm rheostat. The
current flows through the milliammeter,
KS-6208, R-6 20-ohm rheostat, through
239-A vacuum tube filament No. 2, through
R-4, an 8-ohm grid biasing resistor,
through the filament of 239-A vacuum tube
No. 1, through R-3, a 24-ohm biasing re-
sistor, and back to the negative terminal
of the battery supply.

In order to establish a definite ground
potential on the unit, the negative side of
the battery line is connected to a common
ground. The plate voltage is taken from
a 90-volt supply. This is reduced to 45
volts by resistor R-5, which has a resist-
ance of 37,500 ohms, connected to the
plate of vacuum tube No. 1. The phte
potential of the second tube is supplied
through the primary winding of the output
transformer, T-l, and since the resistance
of the transformer winding is relatively
low, the effective voltage applied to the
second tube is approximately 90 volts.

The necessary negative grid potential for
the first vacuum tube is produced by tak-
ing a drop off the 24-ohm series filament
resistor connected in the negative side of
the No. 1 tube filament. The potential
thus taken off is approximately 6VL> volts
negative. The grid bias for the No. 2 tube
is produced by tapping off the voltage
drop produced by a filament current flow-
ing through the 24-ohm series resistance,
the 24-ohm resistance of the No. 1 tube
filament, and the 8-ohm series resistance
connected in the negative side of the No.
2 tube filament. A negative drop of ap-

December, 1929

The Motion Picture Projectionist

Schematic of Western Electric 49-A amplifier.

proximately 9.5 volts is thus produced as
a grid bias for No. 2 tube. The negative
bias will be affected if the "F" batteries
are not fully charged.

The following action occurs during the
operation of the 49-A amplifier : Assume a
light flux entering the photo-electric cell
equal to the light passing through un-
modulated sound track. A steady current
of definite value will, under this condition,
flow from the 90-volt battery source
through the y2-megohm coupling resistor,
through the photo-electric cell, and return
to the battery. This steady current flowing
through the V^-megohm resistance causes a
voltage drop which is applied to the cou-
pling condenser and therefore to the grid
of the first vacuum tube.

The potential on the grid of the tube
will be increased or decreased, depending
upon the direction of the current through
the Vs-megohm resistance. The grid po-
tential will increase, because a time inter-
val is required before any disturbance in
the grid circuit can leak off through the
10- megohm resistor connected between the
grid and condenser and to the negative
battery supply. It is obvious that any
fluctuation of current through the Vs-
megohm coupling resistor will cause a
proportionate fluctuation in the grid po-
tential of the first tube, the limiting factors
being the intensity of the change and the
time interval, as well as the characteristics
of the several units comprising the cir-
cuit.

Any change in the grid potential of the
No. 1 tube will, of course, cause a simi-
lar fluctuation in the plate current of the
tube. The alternating current component
of the plate current passes through the
1 -microfarad blocking condenser, which is
connected in series with the primary side
of the interstage transformer. The A. C.
component will, of course, traverse the
primary windings and return to the fila-
ment of the No. 1 tube.

As previously pointed out, the D. C.
component is supplied through the 37,500-
ohm resistance. The potential of the A. C.
component passing through the primary
winding of the interstage transformer is
increased in proportion to the ratio of
transformation of this unit and is repeated
into the grid circuit of the second vacuum
tube.

The electrical pulsations are repeated
through the No. 2 tube. In the case of
No. 2 tube, both the A. C. and D. C. com-
ponents pass through the primary winding
of the output transformer, as no blocking
transformer is required because an iron
core in the output transformer, the opera-
t'on of which is not affected by the mag-
netizing current of the D. C. component,
the transformer being designed to operate
under these circuit conditions.

The amplified A. C. component is re-
peated through the output transformer,
and the signal voltage is impressed across
the output terminals of this device. The
final level of the amplified energy is ap-
proximately 5Db. when the initial signal
voltage is generated by a normal photo-
electric cell receiving light impulses which
are modulated 100 per cent.

Testing Vacuum Tubes

ON many occasions it is the duty of
the projectionist to test vacuum
tubes for internal short circuits. A pair
of headphones and a 4y2-volt C battery
are used for these tests. The 239-A vac-
uum tubes have two heavy tips and two
lighter tips. The former are connected
to the filament, and the latter are connected
to (the grid and plate.

Hold one testing tip to the grid and
the other to the plate terminal of the tube.
If the tube is in good condition, no click
will be heard ; but if clicks can be heard,
there is a short circuit between the grid
end the plate. Then, while still holding

one testing tip on the grid, touch the other
to either one of the filament terminals.
A click again indicates a short circuit.
Be sure not to use a testing voltage higher
than the filament voltage of the tube being
tested, or the filament may be accidentally
burned out.

Some tubes develop sporadic short cir-
cuits which manifest themselves only now
and then. To find such defects, one should
gently tap the tube while testing, holding
it in a horizontal position, and turning it
around gradually. For such test it will
be found handy to use clips on the ends of
the phone cords, which are snapped to the
tube tips, which enables one to manipulate
the tube more easily. Vacuum tubes which
have internal short circuits must be dis-
carded immediately.

Loose Tube Bases

Many vacuum tubes have been discarded,
I have found, because they become loose
in their base, especially if they are in-
serted and removed from the sockets fre-
quently. The cement holding the glass to
the bakelite base sometimes dries out so
that the glass cracks and loosens. There
is then danger of twisting the wires inside
of the base when inserting or removing the
tube from a socket, and such twisted wires
would result in a short circuit. Tubes
otherwise in good condition may develop
this condition, but it is ' not necessary to
discard them, as a simple and effective
repair may be readily made.

Wrap a layer of adhesive tape partly
over the glass and partly over the top
of the base, as shown in the accompany-
ing illustration. This will prevent the
tube from being turned around in the base,
although care should nevertheless be taken
when removing it and reinserting it in
the socket.

Another remedy for this trouble is to
scrape' away the surplus cement protruding
above the base, and as much as possible
between the base and the tube. Then apply
some "New Skin" or collodion, letting it
run down between the bulb and the base,
and permitting a liberal film to dry on
the outside over both.

Use of Soldering Irons

Every projection room where sound
equipment is installed should have a good
electric soldering iron on hand. In am-
plifier circuits it is absolutely essential that
all connections be mechanically and elec-
trically tight. If this is not the case, there
may be considerable loss of energy due

Methods of treating Idose vacuum tubes.

The Motion Picture Projectionist

December, 1929

MAGNETS

DIAPHRAGM

Left: Magnets and diaphragm of headphone. Right: Headphone with cap and
diaphragm of one earphone removed.

to high resistance joints, or reproduction
may be noisy due to loose connections.
A soldering iron for use on amplifier
circuits must have a long, narrow nose to
enable the user to reach into places which
are inaccessible with a heavy iron ot a
kind used bv tinners. Some sort of rest

is necessary to lay the hot iron on while
it is not in use. Recently a serious film
fire occurred due to negligence in laying
down a hot soldering iron on a rewind
bench. It is essential that such irons be
protected with a hood, so as to avoid any
such possibility.

Sound Projection Hints

Recently I visited one theatre and found
the sound volume to be very low, during
the presentation of a disc sound accompani-
ment. After a brief check it was found
that the fader contacts were very dirty.
Cleaning the contacts restored the volume
to normal.

During a visit to another theatre, the
signal buzzer in the projection room
(controlled from the observer's station in
the audience), was picked up and could be
heard in the sound reproduction. This
trouble was eliminated by removing the
phone and signal, and installing them else-
where in the projection room.

The success of sound pictures is due
to proper presentation without interrup-
tions. It is remarkable how the industry
has handled this new development and has
achieved so much attainment. Managers
know more about motion picture projec-
tion now than ever before. Not so long
ago, it was a general habit for a manager
to go to the house phone, during an inter-
ruption in the performance, and request
the projectionist to give him a detailed re-
port about the trouble; but now it is en-
tirely different. The manager realizes that
during trouble in the projection room the
projectionist's time is occupied in locating
the trouble instead of answering the tele-
phone giving an explanation of the inter-
ruption, and in many instances the man-
ager has greatly assisted by visiting the
projection room, and finding out the true
facts about the interruption.

With the success of sound pictures comes
the elimination of many old practices. One
of these items is the ringing bell of the
theatre inter-phone. These bells must be
muffled, so that they are not an annoyance
to the audience. Theatre patrons must not
be conscious as to the certain operations
of the theatre. Another annoyance to the
audience is the signal system. We realize
the importance of the signal system in
theatres where stage attractions are pre-

Method of testing

for noisy "B"

battery

sented. It is imperative that all buzzer
signals be muffled so that they are not per-
ceptible to the audience.

While equalizing the volume of both
sound projectors, it will be found that by
using the cut-out key on the fader this
adjustment can be made much easier than
by using the dial on the fader. Many times
noisy reproduction can be traced to the
first tube in the 41 -A amplifier not mak-
ing proper contact.

A rectifier tube may become paralyzed
on high volumes. If the amplifier cuts off
during effect records, it would be best to
check carefully the rectifier tubes. Systems

picking up A. C. hum and mechanical
noises from machines, and decided noises
picked up from marquee flashers, may be
eliminated by disconnecting the ground to
the projector base from the grounded side
of the A. C. supply.

It is imperative that the coupling be-
tween the 5S5-W receiver and the horn be
kept perfectly tight, otherwise a blasting
noise will be perceptible. If the Movie-
tone optical system lenses and exciter
lamps are allowed to become dirty, the
quality and quantity of sound will suffer.

Testing "B" Batteries

Two 45-volt dry B batteries are used
in the photo electric cell and pick-up am-
plifier circuit each sound projector with
W. E. systems. Although in a few cases
dealers resort to the amperage test on B
batteries, such a test means very little
and does not show their true condition.
The only accurate test on B batteries is
a voltage test. Each cell must be tested
separately. B batteries should never be
tested for voltage after they have been
standing idle for some time, for when
standing idle they recuperate to some ex-
tent and during the first few minutes of
their subsequent use they will produce a
higher voltage than they will after being
used for several minutes.

Noisy B Batteries

When 45-volt B batteries drop down
to 37 volts, they become noisy. Even new
dry B batteries may sometimes be noisy.
Noise in B batteries is caused by fluctua-
tions in voltage, resulting from poor or
defective cell insulation which is not en-
tirely moisture-proof ; by the quality of
the compound used in the cells, or by im-
purities in this compound ; by faulty cell
construction, and by loose internal con-
struction.

Every new B battery should be tested
before installing in the circuit, as shown
in the accompanying illustration. Connect
a set of headphones in series with a one-
microfarad condenser across the positive
and negative terminals and listen for noise.
It is imperative that a one-microfarad con-
denser be in series with the headset. Be
sure that the connections between battery
terminals and headset are perfectly tight,
as any slight movement in connections
will cause a noise in the phones, and result
in incorrect deduction from the test.

H & C and Sunlight Arc Lamps

Arc

Amper-

age

Size

Kind

Positive

9m/m x 20"

Nat'l H. I. White Flame
Projector

Negative

5/16 x 9"

Nat'l Orotip Cored Pro-
jector

NATIONAL HIGH IN-

Positive

llm/m x 20"

Nat'l H. I. White Flame
Projector

TENSITY PROJECTOR
COMBINATIONS

Negative

11/32 x 9"

Nat'l Orotip Cored Pro-
jector

100-120

Positive

13.6m/m x 20"

Nat'l H. I. White Flame
Projector

Negative

H x 9"

Nat'l Orotip Cored Pro-
jector

ecember,

1929

The Motion Picture Projectionist

RCA SHOWS PORTABLE
SOUND REPRODUCER

RCA PHOTOPHONE, INC., has
demonstrated recently a new port-
able sound picture reproducing apparatus
which is designed for use in the educa-
tional field. By means of this portable
projection apparatus more than 250,000
schools, colleges and universities ; 200,-
000 churches, clubs and lodges, and the
large industrial organizations will be
enabled to provide the foremost lecturers,
statesmen, scientists and industrialists in
sight and sound, bettering, from economic
and practical aspects, the printing press,
lecture platform and radio studio.
Technical Data

Technically, the RCA Photophone
portable sound picture reproducing equip-
ment consists of a projector designed to
accommodate standard 35 mm. film. The
projector is designed to operate from
a power source of 110 volts, 60 cycle
alternating current, and has a standard
sound film speed of 90 feet a minute. A
picture 6 by 8 feet can be projected at a
distance of 50 feet; pictures of other
dimensions are possible with different
lenses. In all its connections, the new
equipment is foolproof with non-inter-
changeable plugs preventing error in con-
nections.

Ruggedness is an outstanding feature
of the new device. It is capable of with-
standing the severest conditions of_ travel
and attendant vibration, maintaining its
adjustment at all times.

A. C. Throughout

The amplifying system is alternating
current-operated, adaptable to direct cur-
rent. Equipment similar in every detail
to 'RCA Photophone apparatus supplied
for sound-on-film operation in the world's
largest theatres is furnished, including a
new improved volume control allowing
adjustment from zero to maximum in
steps of 2 TU. Rectifiers furnish the
necessary direct currents. One of the ex-
clusive elements of the equipment is ac-
commodation in the amplifier for a second
projector. This arrangement also pro-
vides a sound changeover switch, as in

regular theatre installations, for chang-
ing from one projector to the other.

The loudspeaker is of an improved de-
sign capable of giving excellent speech
intelligibility in any room or hall where
a person speaking can be understood.
Provision is made for mounting the
speaker behind the picture screen.
Similar to Theatre Model

In all its details, the new RCA Photo-
phone portable duplicates the apparatus
developed for sound projection in the
theatre equipments of that company. The
picture projection element of the system
insures an excellent screen picture ; the
sound components provide sound, speech
and music in perfect synchronism and
with fine tonal quality.

Because of its standard design, the
RCA portable projector can accommodate
any talking film recorder in the present
development of the art. A vast store of
educational and institutional films is al-

Interior of RCA projector

ready available; others are now in pro-
duction, and it is a positive eventuality
that, as the greatest performers of the
world's stages have flocked to the micro-
phone, so will the geniuses of the arts
and sciences record their knowledge and
experience.

Cam for Starting- Line
J \

Carriage
Y^Feed Nut Lever

14*5=3

Synchronous Motor 33% R.P.M.

For 80 R. P.M. Recording Use
Round Belt

^—Playback Mfntiny
Recording Cutter
7 -*- J Mounting

Perforatedmelt
for Synchronised

" Camera
V/ork

The new Presto recorder embodies many improvements

Amplifier for RCA portable

PRESTO RECORDING
MACHINE

HE salient feature of the Presto
Recording Machine is its vibration-
less construction accomplished through the
simple expedient of a belt drive separat-
ing the power unit from the recording
head. By this simple and at the same
time thoroughly mechanical construction
the need of expensive filtering devices so
necessary in geared constructions — and at
best inefficient — is at once eliminated and
there is provided a smooth, even, perfectly
regular transmission to the recording
head by which the slightest vestige of
vibration is eliminated at the essential
point.

The machine is available for regular
recording at 80 r. p. m. or ZZYz r. p. m.
for synchronized picture work. The
change over is practically instantaneous.
The belt drive for synchronized work is
of such design and construction as to in-
sure positively the established ratio and
to maintain such ratio under any and all
conditions.

In fact, the construction is such as to
make the machine almost universal inas-
much as any desired feed can be made
available by the simple substitution of a
pulley on the recording end.

A vital constructional feature is the
turntable tapered bearing which is self-
aligning and automatically adjustable to
wear without the need of end-thrust take-
up. The bearing is a fit when made, re-
mains a fit and there is no possibility of
any play developing.

A convenient feature is a simple cam
means for establishing a positive cutting
starting point. The cutter point is
dropped on the wax at the desired start-
ing point and the simple operation of set-
ting a stop against the cam face auto-
matically produces the starting groove
and the feed then proceeds at the pre-
determined rate. For straight recording
a hand lever operation cuts the spiral
groove at the end of the record.

A play-back is provided on the feed
slide whereby immediate testing can be
made without removing or disturbing the
cutter head, means being provided for en-
gaging or disengaging either the cutter or
the play-back.

The Motion Picture Projectionist

ecember,

1929

e Laboratory

" Shield Grid " Amplifiers

UNTIL very recently but little work
had been done with the "shield
grid" tube (four element), for audio fre-
quency amplification, although it is well-
known that this type of tube does the work
of two or three ordinary tubes in radio
frequency amplification. The use of a
shield grid tube gives rise to a greater
voltage amplification per single tube than
does any other commonly known type tube.

We are advised by some of our engineer
friends that it is impossible to use the
shield grid tube as an audio frequency am-
plifier. Despite this pessimistic outlook,
however, the engineering staff of Radio-
vision Corp., New York City, has suc-
ceeded in amplifying the potentials
generated as the result of light falling on
the elements of a photo voltaic cell (liquid
filled), used in their latest sound picture
system.

By coupling the photo voltaic cell with a
low impedance transformer (primary), the
secondary of which is connected directly
to the control grid of the tube, and there-
after using the conventional resistance-
coupled amplifier, using shield grid tubes,
they have succeeded in building a very
efficient unit which gives rare tonal quali-
ties. We are advised also that the RCA
Photophone, Inc., has recently built a more
efficient sound picture amplifier which em-
ploys shield grid tubes.

The advantages of shield grid tubes are :
(1) the reduction of noises due to inter-
stage coupling, (2) facilitate the use of
A. C. operation throughout, avoiding the
use of cumbersome batteries and their at-
tendant care, and (3) amplifiers built with
shield grid tubes require but very little
space, as compared with other type am-
plifiers. We prophesy at this time that
the audio frequency amplifiers of the future
will be equipped with shield grid tubes,
and their introduction into projection rooms
for sound pictures will be a matter of
course.

Colored Positive Stock

PRIOR to the advent of sound pictures,
it was a common thing for certain
portions of prints to be dyed (colored), in
order to obtain various effects through
shading. These effects were intended to
enhance the pictorial value of the subject
being shown on the screen. Xow that sound
pictures have become so popular, the lack
of colored films has been the subject of con-
siderable discussion among technical men.
Not that it is impossible to produce colored
films with sound accompaniment, but only
two systems lend themselves easily to color
sequences. These are : ( 1 ) sound accom-
paniment on discs, and (2) the variable

•Conducted by SAMUEL WEIN-

area (saw tooth), method recording such
as is used by RCA Photophone.

With the variable area method of record-
ing there is no difficulty in reproducing
sound from film for the reason that the
light from the exciting lamp passing
through the film bears the same ratio
between the portion that is almost all trans-
parent and that portion which is almost
entirely covered by silver emulsion.

In the case of the variable density
method, we find that the light passing
through the brighter portion (transparent),
of the sound track is much more affected
by the dyestuff in the film than are the
darker portions of the sound track. There-
fore, the entire ratio of light falling on the
photo electric cell is considerably de-
creased as a result of the use of dyes,
which act as a light filter. This filtering
action distorts the wave form of the sound
as reproduced by means of the p.e. cell.

Two methods of solving this problem
come to mind : ( 1 ) the use of a dye
which will permit the proper amount of
actinic light falling on the p.e. cell, giving
the maximum output in the cell as a result
of light passing through the "light filter"
(blue has been used in experimental work),
and (2) by means of a greater "photo-
graphic contrast." thus securing a greater
change in the p.e. cell. Both methods still
are the subject of considerable experi-
mental work, and producers are bending
every effort to perfect a process which will
insure consistent productions of film which
will not distort the wave form.

Recently the Eastman Kodak Company
announced a series of tinted stock which
was the result of extensive research along
this line. This Eastman tinted stock repre-
sents an advance in the right direction,
and it is fairly certain that Eastman
workers will add materially to the art in
the very near future.

" Electrified " Amplifiers

THE modern trend for engineers in
talking motion pictures is the com-
plete electrification of the amplifying units.
By "electrification" reference is had to the
entire elimination of batteries. The elec-
trification of radio sets and amplifiers is a
common thing to-day, but the electrifica-
tion of amplifiers for talking motion pic-
ture systems is still the subject of ex-
perimental work by the engineering staffs
of the various firms engaged in this field
of endeavor.

The Exciting Lamp

We have recently witnessed two methods
of battery elimination for this purpose.
The methods were (1) the use of rectifiers
and (2) the use of coarse filaments in the
exciting lamp.

A prominent manufacturer has recently

placed at our disposal a complete rectifier
to handle any current and voltages avail-
able for exciting lamp by any of the avail-
able talking motion picture systems. This
rectifier has been in constant use for over
a period of several months, without any
tendency to difficulties on the part of the
rectifier, nor any requisite attendance on
the part of the projectionist to this device.
The second method is the use of a special
exciting lamp made for this purpose. From
all outward appearances the exciting lamp
is that of the conventional form, save for
details in its filament. This special excit-
ing lamp is fed from the "raw A. C."
without any intermediate rectification. It
was found by experiment that a heavy or
coarse filament in the use of an exciting
lamp will not correspond in illumination
(not visibly), to the 60-cycle current, and
therefore will have no effect on the photo
electric cell. It is only the fine filaments
that can readily be seen to vary with the
60-cycle variations in the line, and which
therefore affect the photo electric cell.

Rectifiers

The company to which we have already
referred in this text, has designed a special
rectifier which we have had under observa-
tion for several months in a New York
City projection room. This rectifier was
designed to give enough current to supply
the current for the filaments of three 239-A

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Arrows trace path of film which passes

aperture boih laterally and vertically.

New process not yet perfected for

professional use

December, 1929

The Motion Picture Projectionist

tubes on the 41- and 42- A amplifier board,
as well as the potential for the exciting
lamp and including the potential for the
field windings on the 555-W receiver.

This amplifier gave no perceptible "rip-
ple" in the loud speaker unit, even though
the projectionist had his ear close up to
the speaker unit. This has been in use
for several months and the weekly reports
are that it gives satisfactory results with
no attention on the part of the projec-
tionist to this rectifier.

Electrified Amplifiers

Here the amplifier panel consists mainly
of a plurality of screen-grid tubes, all
operating on A. C potentials. These tubes
are obtainable in the open market. The
circuit used is one commonly known to the
engineers ; it is only a matter of adapting
the tubes for the particular purpose.

The Royal Amplitone Corp. has recently
demonstrated a commercial amplifier using
this method of electrification of amplifiers,
with the circuit having been designed by
Mr. R. Miehling.

Special Methods

From a technical viewpoint, it is well to
remember that the photo electric cell itself
is a rectifier, and in some special circuits
it is possible to use the conventional
exciting lamp fed from the raw A. C.
lines, with, of course, a proper resist-
ance in its circuit to adjust the proper
current to it. The photo electric cell
operates as a rectifier, and this is connected
with an electrified set, with the inclusion
of a proper amplifier to further rectify
the A. C. ripple set up in the photo electric
cell circuit, from the exciting lamp.

Riggs Circuit Eliminates Negative Grid Bias

ANEW amplifying circuit of radically
different design than any now in com-
mon use in the radio and sound picture
field has been demonstrated in New York
by Dr. Alger S. Riggs, who has already
made many important contributions to the
electro-technical arts. This new system
eliminates negative grid bias, according to
Dr. Riggs, and several authorities in the
art who were present at the New York
demonstration substantiated this claim.

The apparatus, according to a prominent
patent attorney, does not include the use
of negative grid bias, push-pull system, grid
leak and condenser, neutralization and
balancing and regeneration. The recent
demonstration of this new system showed
the use of the Riggs circuit with a radio
receiving set, but there is no apparent good
reason why the same principles may not
be applied to the sound reproducing
apparatus.

Reports from the demonstration have it
that each stage was tested with a voltmeter
and all revealed positive bias. The
engineers, it was said, admitted that Dr.
Riggs showed the circuit could do every-
thing he claimed for it. The following
general explanation was made by Dr.
Riggs :

Eliminates Negative Bias

"In general, the system as at present
conceived and evolved consists essential-
ly of a fundamental and revolutionary
method of securing amplification by the use
of electron discharge devices. Among other
things, the system displaces the necessity
of utilizing negative C bias throughout. In
fact, in the major portion of the application
of electron discharge devices the electron
stream is not controlled by the grid at all.
Far Sound Pictures

"The radio set demonstrated does not use
(a) negative C bias, (b) tuned radio fre-
quency and (c) grid leak and condenser.
As I demonstrated it, the set was in its
semi-laboratory form, no production or
design engineering having been applied
toward its completion."

It is claimed that the Riggs system
covers more than a radio broadcast re-
ceiver. Its sponsors declared that, in view
of the revolutionary principles involved,
broad patents will be granted covering the

use of the system in radio receivers, radio
broadcast transmitters, commercial radio-
telephony, commercial radiotelegraph)-, land
line telephone repeaters, specific high ac-
curacy frequency measurements, amplifica-
tion of extremely high radio frequencies
and motion picture sound recording and
reproducing apparatus.

alternations, of an A. C. source. In other
words, it was found that if a thin filament
is used in the exciting lamp, it would cor-
respond to the 60-cycle A. C. source ; but
on the other hand,, if a husky filament is
used, it will be found to be insensitive to
the 60-cycle variation, i. e., optically speak-
ing, and so the photo electric cell can be
used in the circuit with which a raw A. C.
is fed to the exciting lamp.

Use Huskier Filament

In order to affect the photo electric cell,
the filament of the exciting lamp must be
sensitive enough to respond to the 60-cycle
A. C, thus giving rise to a ripple. Thin
filaments do respond in this fashion ; but
coarse filaments do not. And so the re-
placement of the thin filament by the coarse
filament is now the subject of extensive
and intensive experimental work.

We have recently witnessed a demon-
stration where raw A. C. from the source
of supply was reduced to 10 volts and
about 7J/2 amperes, in which the horn pro-
duced only a slight ripple. In fact, the
ripple was audible only if one held his ear
very close to the speaker unit.

New Exciting Lamp —
Battery Eliminator

SfNCE the publication of results of ex-
perimental work looking to the elimi-
nation of battery potential for the exciting
lamp, we have discussed with several
workers divers means of accomplishing
this end. Of the various experiments
tried and methods advocated, that which
we are about to describe is, in our opinion,
the simplest of all and the least expensive.
The principle involved in this battery
eliminator is the insensitiveness of a heavy
filament in a lamp to the ripple, or 60-cycle

Eyestrain

There have been endless complaints at
different periods in our history of eye-
strain, headache and a host of associated
evils due to various optical defects which
we have successfully eliminated. Let us
grant that all these claims are scientifically
ill-founded. The fact remains that a pa-
tron who sits through a picture well below
the standard of optical brilliance to which
he has been accustomed will be conscious
of a definite lack in the entertainment value
of the show. He may not analyze it, but
his feeling of satisfaction will be impaired
nevertheless. If we do not wish to hear
a recurrence of these complaints from big-
oted and prejudiced quarters, we must rem-
edy the defects which have unavoidably
been introduced.

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PROJECTION ROOM

ENGINEERING LABORATORY H3 ^t;: |

Layout of projection room in ERPI laboratory.

The Motion Picture Projectionist

December, 1 929

Ask the Projectionist
Who Uses

**>

Them /

*■*•>

STRONG

Automatic
Reflector

ARC LAMPS

-j>

For SaZe fey Trustworthy Independent Supply
Dealers Everywhere

Export Office — 44 Whitehall St., New York City, New York

fhe Strong Electric c<

2 501 Lagrange St. Toledo, O.

Universal Film Splicing

Machine

MODEL NO. 3 Pat. March 22:22

First-Class Results on New or Old Film
Permanent Gauge No Adjusting

FOR THEATRES, EXCHANGES
LABORATORIES, SCHOOLS

Price $6.00

GENERAL MACHINE CO., INC.

816-826 East 140th St.. NEW YORK, N. Y.
For sale by all Supply Dealer*

E. R.P.I. Acoustic Bureau
Serves Theatres

ACOUSTIC analyses of more than
500 theatres have been made during
the last six months by the special acoustic
department of Electrical Research Prod-
ucts under the direction of S. K. Wolf,
acoustical expert. The work of organiz-
ing this department was started a long
time ago but any announcement of its
formation and operation has been care-
fully withheld until important fundamental
research and development work had been

Disc Pick-up Process

(Continued from page 23)

distance covered each side of center by the
moving contact arm, the greater .will be
the voltage generated. But the amount
of motion is limited by the spacing be-
tween grooves on the record and the short-
ening of the gap is limited by the fact that
the magnetic field will pull the armature
over to it unless the rubber is made very
tight.

This action of the magnetic field on the
armature is in the nature of a negative
spring but, contradictory as it may 'sound,
is not equivalent to mass. If the spring
action of the rubber dampers is not suffi-
ciently strong to prevent it, sticking of
the armature will occur on either side of
the gap, under which condition the unit
is inoperable. An ideal condition would
be had if the action of the rubber exactly
counterbalanced that of the field at all
points. This would result in no resonant
frequencies and would show preference to
low frequencies. But such a condition
could not be obtained except in a labora-
tory and even then the adjustment would
be off in a short time, as soon as the rub-
ber "set" a little.

Unlike loud speakers, the dynamic prin-
ciple is not advantageous in pick-ups. The
dynamic speaker is capable of more vol-
ume because the amount of permissible
motion of the cone is several times as
great as that in the magnetic type. But
the extreme amplitude of motion of the
moving parts of a pick-up is fixed by the
spacing between grooves on a record, and
the magnetic type is easily adapted to this
amount of motion.

After all, it is immaterial, from an elec-
trical viewpoint, whether the field is varied
or whether the coils are varied. Alternat-
ing flux through the coil is the result in
cither case, and that is what produces the
voltage.

On the other hand the dynamic principle,
applied to the pick-up, is not as good as
the magnetic type since, for a given fre-
quency, the value of voltage is propor-
tional to the amount of motion. This
means that those frequencies below 250
cycles will be slighted in reproduction, the
same as they are on the record. But low
frequencies are cut with a relatively high
amplitude! and consequently, in the mag-
netic bridge type, these frequencies are
accentuated because, unlike the dynamic,
the voltage produced by the bridge prin-
ciple goes up faster than the amplitude of
motion.

December, 1929

The Motion Picture Projectionist

completed and until some definite accom-
plishments could be pointed to.

The department at present consists of a
staff of 17 men under Mr. Wolf's direc-
tion. Behind its operations are the re-
search facilities of the Bell Telephone
Laboratories and the more than 750 in-
stallation and service engineers and tech-
nical inspectors of Electrical Research
Products who aid in making surveys and
collecting statistical material. In every
case where an acoustic analysis has been
made the department has offered detailed
recommendations for treatment to over-
come any difficulties caused by theatre con-
ditions.

The department is enabled to make sug-
gestions for acoustic improvements, un-
hampered by obligations to the use of any
particular material. Complete files of data
on all acoustic materials are maintained,
and the particular material or combination
of materials may be selected that is best
adapted to the particular conditions in each
theatre. These conditions include a con-
sideration of the cost and appearance in
addition to the acoustic requirements.

Revise Reverberation Figures

The work of the acoustic department is
divided into two branches : analysis and
development. The first-named branch is
devoted to field work in the practical analy-
sis of theatres and in service to the in-
dustry. The latter is devoted to research
work and the development of acoustic
knowledge.

The work of the development branch
has already resulted in important findings.
It has been determined that the time of
reverberation for best acoustic conditions
in a sound theatre does not correspond to
the figures which have long been accepted
by acoustic authorities ; and a new figure
has been determined. This finding has
been checked by a thorough study of more
than SO sound theatres which are known
to possess excellent acoustic qualities, in
addition to 500 theatres needing acoustic
correction. To carry on its research and
experimental work the development branch
has fitted a theatre in Brooklyn as a labor-
atory where tests and examinations in good
and bad acoustics are now carried on.

"The most important factor in good
sound reproduction is the time of rever-
beration," declared Mr. Wolf in describ-
ing the work of his department. "This,
defined in lay terms, is the length of time
the sound remains audible. It is difficult
to give out general rules for theatre con-
struction and equipment because each
theatre presents an individual problem and
it would be misleading to say that any
single rule or set of rules could be applied
without exceptions.

Square Auditorium Best

"Generally speaking, the theatre with an
almost square auditorium reproduces sound
with the best results. The theatre in which
it is most difficult to get good sound repro-
duction is the long, narrow theatre with a
low ceiling. The presence of rugs and
carpets improves sound reproduction be-
cause they not only absorb sound but lessen
the noise caused by movements in the
aisles. Seats can make a great difference
in good or bad reproduction. Without

Standard Equipment

AND OTHER GREAT CIRCUITS

si tciriii cy rca rhctcrhcne,

INC., CN ALL RCA INSTALLATIONS

WALTER

*V PATENT PENDING J

IT Delivers

50% More Light

Sharper Definition

Perfect Sound

No Fadeaway

BRILLIANT PRCJECTICN
WITH LCW INTENSITY

The logical screen for your theatre

Write for Booklet and Sample

WALKER SCREEN CO.

85— 35th Street

Brooklyn, N. Y.

going into a maze of details we can simply
lay down the general rule that a seat
should be able to absorb nearly as much
sound as an individual person. Heavily
upholstered seats approach this condition
and permit good reproduction with either
large or small audiences, a condition not
obtained in theatres with wooden seats.

"More and more, we find, exhibitors are
realizing the importance of good sound
reproduction and are giving attention to
the factors that contribute to it. In this
respect we are able to offer them unbiased
service. We can make a study of each
theatre individually and make recommenda-
tions accordingly. The requests for co-
operation that we are receiving from
theatres is the best evidence of how much
appreciation there is for this pioneering
work.

Notice

IN our advertisement in the
November issue of THE
MOTION PICTURE PROJEC-
TIONIST our address was in-
correctly stated as 451 — 39th
St., Brooklyn, N. Y.

We wish to direct attention
to our correct address listed!
below.

MACY MANUFACTURING CORP.

Largest Horn Makers Supplying
the Theatrical World.
1451 — 39th Street, Brooklyn, N. Y.

The Motion Picture Projectionist

ecember,

1929

IMPERIAL

MG Sets

akePossiblf

Standard

Imperial Two Bearing M-G Set

QUALITY PROJECTION

because they contain several Im-
perial features that contribute to
better projection.

This new standard is the result
of our effort to develop a product
that would give Projectionists the
best results possible.

The following; are four outstand-
ing features.

1. Quiet operation
without vibration.

2. Heavy overload ca-
pacity for short
periods.

3. Constant voltage at
Arc.

4. Reliability.
In checking over,
you will find
that they are
ALL required
in order to

render the BEST RESULTS.
They are built into Imperial M-G
Sets with the result that wherever
Imperial M-G Sets are used they
receive the most enthusiastic
praise and the highest endorse-
ments from Projectionists.

They are priced right and are
suitable for large and
small theatres. Fur-
nished with ball or
sleeve bearings. Motors
up to 30 HP. are self-
start type, requiring no
expensive compensators
saving both first cost
and upkeep. Imperial
also has a line of Bat-
tery Charging

Imperial makes a complete line of Quiet *nd Emergency
Running Motors for Ventilating Systems, Lighting Equip-
Pumps, Elevators, etc. ment.

OUR BUSINESS

CREED

1 Quality

2 Service

3 Right Prices

4 Courteous

Treatment

Distributors write for Territory Rights

THE IMPERIAL ELECTRIC CO.

AKRON

Established 1889
Offices in Principal Cities

OHIO

PHOTO-CELLS, neon lamps, special
■*■ high vacuum or gas filled tubes, and
noise-free liquid grid leaks, manufactured
to specifications.

ARGCO LABORATORIES, Inc.

150 West 22nd Street New York City

P. A. C. Luncheon to
Pres. Canavan

{Continued from page 20)
Local Union 182; the practice of inviting
newspaper picture critics to inspect a typical
modern projection room; the matter of
securing daily newspaper publicity for pro-
jection and projectionists; and the compil-
ing and disseminating of general projec-
tion information by the Projection Advisory
Council.

The time for the open forum was un-
avoidably curtailed, but it would seem that
this circumstance did not affect the success
of the affair for the reason that not a little
interchange of information was accom-
plished at the various individual tables on
the floor during the progress of the
luncheon.

P. A. McGuire of the International Pro-
jector Corp. was the general chairman on
arrangements for the luncheon, and he was
materially assisted in his fine work by
Charles F. Eichhorn, Laurence Jones, Les-
ter Isaac, and George Edwards, all of whom
are members of Local Union 306.

In addition to President Canavan's ad-
dress, there follows a complete list of guests
who were present at the luncheon.

President Canavan's Address

In attempting a discussion of the im- .
portance of motion picture projection, one
who has been intimately associated with
this particular branch of the motion picture
industry for many years may be charged
with over-enthusiasm. It is not, however,
my purpose to over-emphasize the relative
importance of projection and the projec-
tionist to this great industry of which we
are a part. Rather do I seek to dispel the
popular misconception of a great number
of people who through lack of information
and understanding of the subject fail to
realize the true importance and significance
of the mechanical presentation of the mo-
tion picture.

To those of us who have a personal in-
terest in this particular subject, there is
great satisfaction when we visualize the
tremendous strides that have recently been
made in the development of projection
room practice and equipment. These re-
cent developments have been of signal
importance to the millions of patrons of
the justly popular motion picture entertain-
ment, and have given a new impetus to one
of America's leading industries. Some
one has well said, "This is the age of elec-
trical entertainment." The vast patronage
with which the motion picture theatres
have been favored is the greatest assurance
that these technical and mechanical devel-
opments have found instant public favor,
and that developments of similar character
will be received with like satisfaction by
the general theatre-going public. The
worlds greatest research laboratories, pre-
sided over by the outstanding scientific and
mechanical minds of our times are at the
present moment bending every effort to-
ward the development and perfection of
the technical side of the motion picture art.
Already we have assurances of the develop-
ment of third-dimension projection to a
commercially practicable point. The me-
chanical development of projection equip-

December, 1929

The Motion Picture Projectionist

ment and projection practices is unques-
tionably destined to play the leading role
in the future development of the motion
picture industry.

With the coming of these vast changes
in projection room practice and equipment,
the members of the projectionist Local
Unions throughout the United States and
Canada are fully alive to the great respon-
sibilities that will devolve upon them and
are preparing themselves by intensive train-
ing and study to meet the changed and chang-
ing conditions in projection problems, come
what may. The theatre-going public, to
whom the motion picture theatre lias come
to be an indispensable necessity, and those
who have hundreds of millions of dollars
invested in this industry, need have no con-
cern regarding the ability of the projec-
tionist to cope with the new projection
problems.

To the everlasting credit of the projec-
tionist, it can be said that he never shirks
his responsibilities. New projection room
equipment, no matter how complicated it
may be, is always a welcome addition to
the projection room, even though past ex-
perience clearly indicates to him that labor-
atory developed equipment brings with it
added worry and work. The projectionist
is more of an idealist than a working man.
He looks upon motion picture projection
as a "specialized art," and is ever striv-
ing to improve the quality of screen enter-
tainment even though it entails a personal
sacrifice. The consciousness that the suc-
cess or failure of the entire screen per-
formance is dependent upon his skill and
its application in the handling of the deli-
cate projection equipment, has a natural
tendency to arouse the projectionist to a
sense of the great responsibility of his pro-
fession. He approaches his task, not from
the standpoint of a worker who is to re-
ceive a monetary consideration in the form
of wages for a given number of hours of
service, but rather from the standpoint of
an artist, mechanically etching upon the
silver screen a series of photographic
images that are unfolding to his movie
audience a visual impression of a story
told with the aid of his mechanical pen.
And at the same time he deftly manipulates
the projection sound equipment in a man-
ner so as to give proper modulation to the
spoken voice in syncronism with the photo-
graphic images, so that the illusion of life
and voice in his story book characters may
be complete.

The introduction of sound presented a
series of problems that were entirely new
to the projection field. To begin with, the
sound equipment had only been subjected
to laboratory tests prior to its installation
in the theatre. These tests had been con-
ducted under uniform and ideal conditions,
by technicians who had developed apace
with the sound equipment.

But theatres could not be re-constructed
so as to make them ideal for the new sound
installations. The physical conditions ob-
taining in many of the theatres were such
that it was next to impossible to achieve
the desired results. Each installation pre-
sented its own particular problems that
could only be solved after subjection to
practical tests. That the original installa-
(Contin<ued on next page)

THE NEW
POWER AMPLIFIER

IN projecting sound to reach large as-
semblages of people in ball rooms, in
the open air, or in rooms larger than
those in the average home, the volume
transmitted must be greater than is ordin-
arily attainable, but without the loss of
tone, quality, or fidelity of reproduction.

The AmerTran Concert Hall Amplifier
is distinguished for its exceptional purity
of tone and exact reproduction of music
and the speaking voice without distortion
under greatly augmented volume. Of
switchboard type construction with in-
terchangeable panel sections, it requires
a minimum of floor space. Being designed
for either direct or remote operation the
amplifier may be located at a distance
from the speaker and from the radio
tuner or other input source of audio fre-
quency. Entirely AC operated; three
stages of audio amplification; uses the
new UX2 50 tubes.

American Transformer engineers are
ready to give you the benefit of many
years' experience. Consult us freely — no
obligation involved.

<<<<<<<<< <<-< <<<<<<<<<

AMtRTRAN

(^oncert <Z7tclLL

AMPLIFIER

?RITE for Bulletin 1077 contain-
ing co~ plete technical data on tha
AmerTran Concert Hall Amplifier
Type 2 5 A, a_ proved by the Under-
writers Laboratories.

Licensed under patents of the Radio Corporation of America
and associated companies for radio, amateur , experimental and
broadcast reception.

AMERICAN
TRANSFORMER COMPANY

178 EMMET STREET, NEWARK, N.J.

"oo' space eS mi"^Uni

°PeratiOQ.Ct °r *emote

4- Three „
a5mP^catioS^esofaiid.o

*beHSes the ne,y Vx ^

sectioot^Seable p^

The Motion Picture Projectionist

December, 1929

ACTODECTORS

THE FISHER THEATRE,
Detroit, Graven & Mayger,
Architects, was built by Fisher
& Company who spared no
expense in getting the finest equipment procurable.

It is significant that ROTH Actodectors — two of them to
be exact — were chosen to furnish direct current for the
projector arcs.

Just as this theatre exemplifies all that is fine in design,
equipment and construction, so does "ACTODECTOR" on a
motor generator mean clear, intense, flickerless projection even
during changeovers.

ROTH BROTHERS & CO.

Division of Century Electric Company, St. Louis, Mo.

1400 W. Adams St., Chicago, 111.

New York Office, 50 Church St.

Distributors in nil principal cities of the world.

Also manufacturers of electric light and power plants

FOR PERFECT SOUND REPRODUCTION ON THE SCREEN
ENCLOSE ALL PORTHOLES WITH

F. S. C.
Optical Crown Glass Plates

Plano-Plano

Will Not Distort

Surfaces With Precision Polish

FISH-SCHURMAN CORPORATION

45 West 45th St. 6364 Santa Monica Blvd.

NEW YORK CITY HOLLYWOOD, CALIF.

tions of projection equipment, for the re-
production and amplification of sound were
not perfect, is not difficult to understand.

After the installation was made, the re-
sponsibility of operating and maintaining
the sound equipment became the duty of
the projectionist who had little knowledge
of the complicated device, aside from a few
hours of operating instruction. This un-
familiarity was not due to his indifference.
There had been no opportunity to secure
the technical information necessary or to
prepare himself for this new responsibility.
From the outset it was apparent there
would be trouble. Many changes had to
be made before the sound equipment meas-
ured up to the exacting exhibition require-
ments of the modern motion picture thea-
tre. The projectionists who pioneered the
introduction of sound have every right to
feel a great satisfaction in the contribution
they made to the development of this art.

The men who have solved these prob-
lems in a practical and highly satisfactory
manner are to be congratulated. They are
deserving of the highest commendation
from the entire motion picture industry
for this splendid service.

The audience cannot be expected to ap-
preciate the painstaking efforts incorporated
into the work of the projectionist in at-
tempting to present for their enjoyment a
faultless screen performance. How are
they to know of the projection problems
to be overcome in producing the screen
results which they expect and demand?
They have no means of knowing that at
each performance more than ten thousand
feet of delicate film of a highly inflam-
mable nature is being driven through the
intricate steel projection mechanisms at a
high rate of speed and that this operation
is repeated as often as eight times in a
single day. Would it matter if they were
to know of the intense heat to which the
film is subjected in passing before the con-
centrated light rays and of the conse-
quences of even a momentary stoppage of
the film under such conditions. How are
they to arrive at an understanding of the
constant care and attention necessary on
the part of the projectionist in caring for
the equipment so there may be no inter-
ruption in the performance? It seems to
me that a proper appreciation of the work
of the projectionist by the theatre patron,
and by others who should be better in-
formed, will not be forthcoming until we
have succeeded in dispelling the popular
misconception that the duties of the pro-
jection room staff are to operate and care
for electrical and mechanical devices which
are automatic in operation and require but
scant attention.

No attempt will be made by me to stress
the mechanical ability of the capable pro-
jectionist. Neither shall I dwell upon the
requisite understanding of electrical phe-
nomena which is indispensable to the solu-
tion of projection room problems. Of his
familiarity with the principles of optics, I
shall only say that without this knowledge,
the splendid image definition which is char-
acteristic of the finished screen perform-
ance would be impossible of attainment,
and the beautiful photographic results of
the skilled cameramen would be wasted.

It is true, of course, that an able pro-
jectionist must be a good mechanic but

December, 1929

The Motion Picture Projectionist

it does not naturally follow that a good
mechanic would be an able projectionist.
My impression of the matter is that real
showmanship is one of the most essential
qualities for the real projectionist. He
must be show-minded in all that the term
implies, with a background of theatrical
experience which will imbue him with that
theatrical spirit, — "The show must go on,"
no matter what may happen. No amount
•of academic training alone could possibly
produce an outstanding projectionist. The
■essentials for good projection are not to be
learned out of books alone. True, the
theoretic approach will be of value to the
novice and will be highly beneficial to the
experienced projectionist ; no man ever
lived who knew as much as he ought to
"know. When a man reaches the point
where he imagines he has all the knowl-
edge he needs, it is a certain indication
of his need of it.

Physical conditions in the construction
of a theatre necessitate locating the pro-
jection room at some point remote from
easy access. It seldom has visitors. In-
deed, the larger theatres are strict in en-
forcement of the rule forbidding visitors in
the projection room. In many cities there
are ordinances which forbid any but a li-
censed projectionist from entering. As a
result the projection room is a sort of
mystery place little known to the average
person. The projectionists live a hermit's
existence while on duty and find their time
well occupied, especially so since the ad-
vent of the audible film which requires
constant care and attention.

When sound is recorded on disc, the pro-
jectionist must be constantly apprehensive
of mishaps for the reason that once the
film and recorded disc are out of syncroni-
^ation, the performance is utterly ruined,
as there is no practical method yet devised
to re-syncronize the disc and film. No
mishap occurring in the projection room
•causes the consternation that is occasioned
when disc and film are not in syncronism.
Sometimes the projectionists are at fault,
hut more often the fault lies in some defect
in the film, the disc, or the mechanical at-
tachment. It is to be expected that the
projectionist will be blamed for any mis-
hap which may occur, especially by the
audience. In the many years that I have
"been connected with the theatre, I have
never witnessed any mishap which so
thoroughly irritates the audience as does
an interruption in the showing of a sound
subject. Under such a condition the
audience becomes restless and gives full
expression to their feelings in no uncertain
manner.

Not so long ago the entire projection
room equipment for the finest theatre
could have been purchased at a cost of
less than $5,000.00; while today suitable
equipment may reach a cost of $50,000.00.
This latter sum would, a few years ago,
have been sufficient to have paid the en-
tire cost of building and equipping through-
out an entire theatre of goodly propor-
tions. It is a pleasure to note that the
better class of theatres have at last come
to a realization of the importance of the

(Continued on next page)

2.5 BI-FOCAL

Super -Lite Projection
Lens

Adjustable
FOR BOTH SILENT
AND SOUND FILM

i/2 & 3/,' Variation in E. F.

AS the name implies this new construction offers the projec-
tionist everything he has been looking for; two focal
lengths in one construction.

By rotating the ring on the lens mount the size of the image
on the screen can be increased or decreased instantly to take
care of the difference between sound and silent film. At the
same time an automatic shifting of the center of picture on
screen with sound film is provided for.

These features have been made part of the F/2 BiFocal
Super-Lite with no sacrifice of the well-known perfect qualities
of the Super-Lite which has been used by the best projectionists
for the last seven years.

h '■-

PROJECTION OPTICS CO., INC.

330 Lyell Ave.

ROCHESTER, N. Y.

U. S. A.

The Motion Picture Projectionist

December, 1929

COLOR

at the price of
black-and-white

JLASTMAN Sonochrome Tinted Positive
Films were developed specifically to add
color to sound pictures at low cost. They
do just that. The sixteen subtle atmos-
pheric tints, bringing new color moods
to the screen, are so adjusted that they
give unusually faithful sound reproduc-
tion. Yet the films cost no more than
ordinary black-and-white positive.

EASTMAN KODAK COMPANY

ROCHESTER, NEW YORK

Complete your sound equipment with a

"BEST"

Rewind Pulley

Takes the place of space collar on Reel

shaft — Crank is not Removed

Manufactured by

BEST DEVICES CO.

2108 PAYNE AVE.

Prist 13.00 at all dealers

CLEVELAND, O.

projection room and are furnishing ade-
quate and modern projectors and equip-
ment, which enables the projectionist to
produce proper screen results. It is to
be regretted that many theatres are still
using inadequate and antiquated equipment.
Good projection requires good projectors.
Poor. screen results will do more to injure
a theatre's reputation and patronage than
any other single factor. Bad projection
and good business are never companions.
Show me a theatre where proper projec-
tion standards are not maintained, and I
shall show you a theatre where business is
in the same category as its projection.

In closing, may I not express the hope that,
in the not far distant future, there may be
a better understanding and appreciation on
the part of motion picture audiences of pro-
jection and its importance in presenting
and emphasizing the visual and audible
artistry of the production staff that has
been so painstakingly incorporated into
the production by the director, the camera-
man, the actor and the technician. A
proper understanding of "projection, a
specialized art" will add immeasurably to
one's appreciation and enjoyment of the
performance. I want to caution all of
you who are projectionists against ever
being satisfied with projection mediocrity.
There is always room for improvement,
no matter what has been accomplished.
Perfection in projection has not been
achieved, irrespective of the splendid prog-
ress that has been made. Let all of us
who are interested in the advancement of
the science of motion picture projection re-
dedicate our purposes to the continuance
of the drive for better projection, a drive
not rooted in selfishness ; an effort not in
the interest of personal gain, but a con-
tribution to the motion picture industry
through co-operation and good will. Let
us spare no effort to enhance the value of
the motion picture as an art by earnestly
and constantly striving for greater appre-
ciation of motion picture entertainment
through the application of the scientific
principles and practices which produce the
highest standards of motion picture pro-
jection, thus giving increased pleasure and
satisfaction to the millions of motion pic-
ture patrons, whose goodwill and patron-
age are indispensable to the future develop-
ment and permanence of the entire motion
picture industry.

List of Guests

Harry Abbott, L. 307; P. M. Abbott,
M. P. News; Joseph Abrams, Le Roy
Andrews, Boston; George S. Applegate,
ERPI ; John Armitage, L. 485 ; L. R. Baird,
L. 384; Frank Baker, Wash., D. C;
Donald Ball, L. 329; Thad Barrows, Pres.
L. 182 ; J. D. Basson, L. 306 ; M. C. Batset,
RCA Photophone; Milton Berkowitz, L.
306; J. Bernheimer, Wash., D. C. ; A.
Bernstein, Publix ; Edward Black, L. 203 ;
Lester Bowen, Int. Proj. Corp.; James
Burke, L. 182; S. R. Burns, Int. Proj.
Corp.

Also James R. Cameron, Pres. William
Canavan of the I. A. T. S. E., Fred Castle,
L. 306; Joe Ciffre, Nat. Thea. Supp. Co.;
Joseph Clayton, L. 306; H. C. Conrad,
Leo Cowley, George Cushing, L. 485 ;
Frank R. Day, L. 306; Oliver De Freitas,
E. De Hart, L. 384 ; George De Kruif, Nat.
Thea. Supp. Co.; Fred J. Dempsey, 1st

December, 1929

The Motion Picture Projectionist

V-P of I. A. T. S. E. ; Albert De Titta, L.
384 ; Harry Dignam, Asst. Pres. of I. A. T.
S. E.; H. Dulborger, L. 384; John Eber-
son, architect ; E. Ederhart, L. 384 ; George

C. Edwards, L. 306; Charles F. Eichhorn,
L. 306; John D. Elms, Fox Grandeur;

B. A. Erickson, Elisha Evans, L. 384.

Also James J. Finn, Motion Picture Pro-
jectionist; Charles Fossa, Boston; J. E.
Francis, RCA photophone; A. B. Freeman,
William Friedman, Ray Gallo, N. D.
Golden, Asst. Chief M. P. Div., U. S. Dept.
of Commerce ; Sam Glauber, Publix ;
Arthur Gray, L. 182; Benjamin Green, L.
307; B. F. Greene, Dept. of W. G. & E.,
N. Y. City; Herbert Griffin, Int. Proj.
Corp. ; John Griffiths, C. F. Grishaber, John
Gulfo, L. 384 ; Peter Haller, J. A. Harding,
H. V. Heck, John M. Hobley, L. 4; E.
Hoffman, Hoffman & Soons Co. ; Fred
Holby, L. 4; Max Hollander, L. 306; J. J.
Hopkins, Publix; T. L. Hopkins, Wash.,

D. C. ; Willard Howe, M. P. Review ; W.

C. Hubbard, Treas. S. M- P. E. ; Charles
Humphrey, Lester Isaac, Pres. Projec.
Adv. Council ; Horace Johns, and Larry
Jones, Sec. P. A. C.

Also Sam Kaplan, Pres. L. 306;
Lawrence Katz, L. 488; Otto Kafka, L.
306 ; T. C. Kennedy, Sam Kessler, L. 329 ;
E .T. Keyser, M. P. Today ; A. Kindleman,
R. C. Kneur, Fred Krause, L. 4; Louis
Krause, I. A. Pa. representative ; W. C.
Kunzmann, Nat. Carbon Co. ; W. D. Lang,
Mgr. Claim Dept. I. A. T. S. E. ; Charles
Levin, Albert Linde, L. 4 ; Boone Mancall,
Motion Picture Projectionists; Frank Man-
drake, L. 384; P. A. McGuire, Int. Projec.
Corp. ; Dr. T. McGuire, W. C. Michel, Int.
Projec. Corp.; John Miller, L. 384; J. A.
Milligan, Associated Publications ; George
Miles, L. 329; B. Morel, L. 306; Morris
Moriarity, L. 273; Dr. Morton, N. Y. C.
Health Dept. ; H. B. Mourier.

Also Charles Parshley, Cambridge; Joe
Pelso, Louis Pirovano, Boston; Major A.
Rasmussum, Vocalite Screen Corp. ; A. L.
Raven, Raven Screen Corp. ; F. H. Richard-
son, W. C. Ricks, Wash, D. G; P. D.
Ries, Joseph Rosen, Boston ; Morris
Rotker, L. 306; G. C. Rowe, Sam Rubin,
L. 488; Irving Samuels, Automatic Devices
Co. ; Henry Schmidt, L. 306 ; C. H. Secor,
S. A. Seifert, L. 203 ; Alvin Seiler, Edward
P. Shalley, M. Shankman, Ben Shylen,
Assoc. Publications ; H. Silverberg, L. 306 ;
Will C. Smith, F. V. L. Smith, J. E.
Soons, Hoffman & Soons Co. ; Wesley
Stanger, M. P. Review; B. Stern, L. 306;
Harold Stern, L. 550; Hirsch Stern, L. 306;
Morris Sternberg, L. 306; J. E. Stewart,
F-P-L; E. T. Stewart, L. 306; Frank J.
Storty, Wash, D. C. ; Frank Sutton, L. 550.

Also Simon Terr, L. 306 ; Charles Thide,
Lawrence Tiferlip, Int. Photog. ; Lewis
Townsend, Rochester, N. Y, ; Charles
Travis, Schenectady; Benjamin Turner, L.
306; Frank Vogel, L. 550; W. E. Waddell,
Fox Grandeur ; George Wedmeyer, L. 384 ;
Lyle Wheeler, L. 306; William Widman,
L. 306; H. C. Wille, S. Winick, L. 306;
William Wolfe, L. 329; John E. Wood, L.
384; and H. Youngswick.

THE BURT REPRODUCER

FOR TALKING MOTION PICTURES

NEW MACY UNIT

The Macy Manufacturing Co. of Brook-
lyn, N. Y, announces a new style ex-
ponential air column horn for public ad-
dress and sound reproduction purposes.
This new type is known as Model S-72 and
was developed for theatres and auditoriums
seating less than 500. . According to its
makers, this latest horn development will
give ample sound and is particularly suited
for delivering- excellent speech results.

Burt Reproducer on Powers Projector